While the automotive industry is taking great strides to make a truly autonomous future a reality, there is still a long way to go before fully autonomous vehicles are on our roads. In the meantime, automakers and technology suppliers are developing...

ABSTRACT

Bacterial flagella are rotating nanomachines required for motility. Flagellar gene expression and protein secretion are coordinated for efficient flagellar biogenesis. Polar flagellates, unlike peritrichous bacteria, commonly order flagellar rod and hook gene transcription as a separate step after production of the MS ring, C ring, and flagellar type III secretion system (fT3SS) core proteins that form a competent fT3SS. Conserved regulatory mechanisms in diverse polar flagellates to create this polar flagellar transcriptional program have not been thoroughly assimilated. Using in silico and genetic analyses and our previous findings in Campylobacter jejuni as a foundation, we observed a large subset of Gram-negative bacteria with the FlhF/FlhG regulatory system for polar flagellation to possess flagellum-associated two-component signal transduction systems (TCSs). We present data supporting a general theme in polar flagellates whereby MS ring, rotor, and fT3SS proteins contribute to a regulatory checkpoint during polar flagellar biogenesis. We demonstrate that Vibrio cholerae and Pseudomonas aeruginosa require the formation of this regulatory checkpoint for the TCSs to directly activate subsequent rod and hook gene transcription, which are hallmarks of the polar flagellar transcriptional program. By reprogramming transcription in V. cholerae to more closely follow the peritrichous flagellar transcriptional program, we discovered a link between the polar flagellar transcription program and the activity of FlhF/FlhG flagellar biogenesis regulators in which the transcriptional program allows polar flagellates to continue to produce flagella for motility when FlhF or FlhG activity may be altered. Our findings integrate flagellar transcriptional and biogenesis regulatory processes involved in polar flagellation in many species.

IMPORTANCE Relative to peritrichous bacteria, polar flagellates possess regulatory systems that order flagellar gene transcription differently and produce flagella in specific numbers only at poles. How transcriptional and flagellar biogenesis regulatory systems are interlinked to promote the correct synthesis of polar flagella in diverse species has largely been unexplored. We found evidence for many Gram-negative polar flagellates encoding two-component signal transduction systems with activity linked to the formation of flagellar type III secretion systems to enable production of flagellar rod and hook proteins at a discrete, subsequent stage during flagellar assembly. This polar flagellar transcriptional program assists, in some manner, the FlhF/FlhG flagellar biogenesis regulatory system, which forms specific flagellation patterns in polar flagellates in maintaining flagellation and motility when activity of FlhF or FlhG might be altered. Our work provides insight into the multiple regulatory processes required for polar flagellation.

ABSTRACT

Two-component signaling systems (TCSs) function to detect environmental cues and transduce this information into a change in transcription. In its simplest form, TCS-dependent regulation of transcription entails phosphoryl-transfer from a sensory histidine kinase to its cognate DNA-binding receiver protein. However, in certain cases, auxiliary proteins may modulate TCSs in response to secondary environmental cues. Caulobacter crescentus FixT is one such auxiliary regulator. FixT is composed of a single receiver domain and functions as a feedback inhibitor of the FixL-FixJ (FixLJ) TCS, which regulates the transcription of genes involved in adaptation to microaerobiosis. We sought to define the impact of fixT on Caulobacter cell physiology and to understand the molecular mechanism by which FixT represses FixLJ signaling. fixT deletion results in excess production of porphyrins and premature entry into stationary phase, demonstrating the importance of feedback inhibition of the FixLJ signaling system. Although FixT is a receiver domain, it does not affect dephosphorylation of the oxygen sensor kinase FixL or phosphoryl-transfer from FixL to its cognate receiver FixJ. Rather, FixT represses FixLJ signaling by inhibiting the FixL autophosphorylation reaction. We have further identified a 4-cysteine motif in Caulobacter FixT that binds an Fe-S cluster and protects the protein from degradation by the Lon protease. Our data support a model in which the oxidation of this Fe-S cluster promotes the degradation of FixT in vivo. This proteolytic mechanism facilitates clearance of the FixT feedback inhibitor from the cell under normoxia and resets the FixLJ system for a future microaerobic signaling event.

IMPORTANCE Two-component signal transduction systems (TCSs) are broadly conserved in the bacterial kingdom and generally contain two molecular components, a sensor histidine kinase and a receiver protein. Sensor histidine kinases alter their phosphorylation state in direct response to a physical or chemical cue, whereas receiver proteins "receive" the phosphoryl group from the kinase to regulate a change in cell physiology. We have discovered that a single-domain receiver protein, FixT, binds an Fe-S cluster and controls Caulobacter heme homeostasis though its function as a negative-feedback regulator of the oxygen sensor kinase FixL. We provide evidence that the Fe-S cluster protects FixT from Lon-dependent proteolysis in the cell and endows FixT with the ability to function as a second, autonomous oxygen/redox sensor in the FixL-FixJ signaling pathway. This study introduces a novel mechanism of regulated TCS feedback control by an Fe-S-binding receiver domain.

Programmed death-ligand 1 (PD-L1/B7-H1) serves as a cosignaling molecule in cell-mediated immune responses and contributes to chronicity of inflammation and the escape of tumor cells from immunosurveillance. Here, we investigated the molecular mechanisms leading to PD-L1 upregulation in human oral carcinoma cells and in primary human gingival keratinocytes in response to infection with Porphyromonas gingivalis (P. gingivalis), a keystone pathogen for the development of periodontitis. The bacterial cell wall component peptidoglycan uses bacterial outer membrane vesicles to be taken up by cells. Internalized peptidoglycan triggers cytosolic receptors to induce PD-L1 expression in a myeloid differentiation primary response 88 (Myd88)-independent and receptor-interacting serine/threonine-protein kinase 2 (RIP2)-dependent fashion. Interference with the kinase activity of RIP2 or mitogen-activated protein (MAP) kinases interferes with inducible PD-L1 expression.

Sperm head shaping is a key event in spermiogenesis and is tightly controlled via the acrosome–manchette network. Linker of nucleoskeleton and cytoskeleton (LINC) complexes consist of Sad1 and UNC84 domain–containing (SUN) and Klarsicht/ANC-1/Syne-1 homology (KASH) domain proteins and form conserved nuclear envelope bridges implicated in transducing mechanical forces from the manchette to sculpt sperm nuclei into a hook-like shape. However, the role of LINC complexes in sperm head shaping is still poorly understood. Here we assessed the role of SUN3, a testis-specific LINC component harboring a conserved SUN domain, in spermiogenesis. We show that CRISPR/Cas9-generated Sun3 knockout male mice are infertile, displaying drastically reduced sperm counts and a globozoospermia-like phenotype, including a missing, mislocalized, or fragmented acrosome, as well as multiple defects in sperm flagella. Further examination revealed that the sperm head abnormalities are apparent at step 9 and that the sperm nuclei fail to elongate because of the absence of manchette microtubules and perinuclear rings. These observations indicate that Sun3 deletion likely impairs the ability of the LINC complex to transduce the cytoskeletal force to the nuclear envelope, required for sperm head elongation. We also found that SUN3 interacts with SUN4 in mouse testes and that the level of SUN4 proteins is drastically reduced in Sun3-null mice. Altogether, our results indicate that SUN3 is essential for sperm head shaping and male fertility, providing molecular clues regarding the underlying pathology of the globozoospermia-like phenotype.

OBJECTIVE

Type 2 diabetes is characterized by increased death rate. In order to tackle this dramatic event, it becomes essential to discover novel biomarkers capable of identifying high-risk patients to be exposed to more aggressive preventive and treatment strategies. hs-CRP and serum amyloid P component (SAP) are two acute-phase inflammation proteins, which interact physically and share structural and functional features. We investigated their combined role in associating with and improving prediction of mortality in type 2 diabetes.

Gastrointestinal (GI) or gut microbiotas play essential roles in host development and physiology. These roles are influenced partly by the microbial community composition. During early developmental stages, the ecological processes underlying the assembly and successional changes in host GI community composition are influenced by numerous factors, including dispersal from the surrounding environment, age-dependent changes in the gut environment, and changes in dietary regimes. However, the relative importance of these factors to the gut microbiota is not well understood. We examined the effects of environmental (diet and water sources) and host early ontogenetic development on the diversity of and the compositional changes in the gut microbiota of a primitive teleost fish, the lake sturgeon (Acipenser fulvescens), based on massively parallel sequencing of the 16S rRNA gene. Fish larvae were raised in environments that differed in water source (stream versus filtered groundwater) and diet (supplemented versus nonsupplemented Artemia fish). We quantified the gut microbial community structure at three stages (prefeeding and 1 and 2 weeks after exogenous feeding began). The diversity declined and the community composition differed significantly among stages; however, only modest differences associated with dietary or water source treatments were documented. Many taxa present in the gut were over- or underrepresented relative to neutral expectations in each sampling period. The findings indicate dynamic relationships between the gut microbiota composition and host gastrointestinal physiology, with comparatively smaller influences being associated with the rearing environments. Neutral models of community assembly could not be rejected, but selectivity associated with microbe-host GI tract interactions through early ontogenetic stages was evident. The results have implications for sturgeon conservation and aquaculture production specifically and applications of microbe-based management in teleost fish generally.

IMPORTANCE We quantified the effects of environment (diet and water sources) and host early ontogenetic development on the diversity of and compositional changes in gut microbial communities based on massively parallel sequencing of the 16S rRNA genes from the GI tracts of larval lake sturgeon (Acipenser fulvescens). The gut microbial community diversity declined and the community composition differed significantly among ontogenetic stages; however, only modest differences associated with dietary or water source treatments were documented. Selectivity associated with microbe-host GI tract interactions through early ontogenetic stages was evident. The results have implications for lake sturgeon and early larval ecology and survival in their natural habitat and for conservation and aquaculture production specifically, as well as applications of microbe-based management in teleost fish generally.

Smart Education And Learning Market Size, Share & Trends Analysis Report By Age, By Component (Hardware, Software, Service), By Learning Mode, By End User, By Region, And Segment Forecasts, 2020 - 2027Read the full report: https://www.reportlinker.com/p05891723/?utm_source=PRN The global smart education and learning market size is expected to reach USD 680.1 billion by 2027. The market is anticipated to witness a CAGR of 17.9% from 2020 to 2027. Demand for smart education and learning solutions is increasing among the growing population in corporate and academic sectors, owing to benefits such as improved education quality and easy access to educational content. Increasing adoption of consumer electronics, such as smartphones, e-readers, laptops, and e-learning applications, has altered conventional education methodology and has enhanced the efficiency of an individual to learn. Additionally, there are enormous opportunities for advancements in the market, owing to improved internet accessibility.Also, the COVID - 19 outbreak has emerged an opportunity for the market with an increasing number of states and countries closing educational institutes. For instance, over 90.0% of the world's students are not attending their schools due to this pandemic, as mentioned by UNESCO (The United Nations Educational, Scientific, and Cultural Organization). Commonwealth of Learning (COL), an intergovernmental organization of The Commonwealth (Canada), has supported educational institutions and governments in building robust distance education solutions for quality e-learning practices. However, lack of awareness among end-users about the latest technologies and inadequate amount of resources for delivering quality education in developing regions is anticipated to hinder market growth.The simulation-based learning segment is anticipated to exhibit the highest CAGR because this mode enables corporate professional and educational institutions to create a realistic experience in a controlled environment.It also allows professionals and learners to practice, navigate, explore, and obtain more information through a virtual medium before they start working on real-life tasks.Growing awareness among people and the rising popularity of smart education are encouraging solution providers to invest in research and development for creating more reliable, better, and cost-effective solutions. Manufacturers are making substantial investments in developing new products for enhancing the user experience.Smart education and learning market report highlights:• Growing demand for smart educational practices can be accredited to factors, such as reducing expenses of online training, curbing geographic challenges in physically attending classes, and time constraints faced by aspirants• Increasing penetration of the Internet of Things (IoT), enhanced internet accessibility, and rapid adoption of mobile technology have encouraged users to adopt smart education and learning solutions• Innovative techniques, such as gamification, Massive Open Online Courses (MOOCs), microlearning, and adaptive learning, which improve the overall educational process, are expected to drive the market over the projected period• North America accounted for the largest market share in 2019 owing to its large consumer base for e-learning methodsRead the full report: https://www.reportlinker.com/p05891723/?utm_source=PRN About Reportlinker ReportLinker is an award-winning market research solution. Reportlinker finds and organizes the latest industry data so you get all the market research you need - instantly, in one place. __________________________ Contact Clare: clare@reportlinker.com US: (339)-368-6001 Intl: +1 339-368-6001

Stephen Sanderson, group inspection product manager and Guven Turemen, group metrology product manager, both from manufacturer Vision Engineering, discusses how manufacturers can ensure the quality of plastic components.

Röchling Engineering Plastics UK is supporting the medical and healthcare sectors with thermoplastic components and materials to assist the NHS and worldwide OEMs.

Laura Wang-Woodford, a U.S. citizen who served as a director of Monarch Aviation Pte, Ltd. (“Monarch”), a Singapore company that imported and exported military and commercial aircraft components for more than 20 years, pled guilty today in federal court in Brooklyn to conspiring to violate the U.S. trade embargo by exporting controlled aircraft components to Iran.

Control Components Inc. (CCI), a Rancho Santa Margarita, Calif.-based company, pleaded guilty today to violations of the Foreign Corrupt Practices Act (FCPA) and the Travel Act in a decade-long scheme to secure contracts in approximately 36 countries by paying bribes to officials and employees of various foreign state-owned companies as well as foreign and domestic private companies.

A Dutch aviation services company, its director and sales manager pleaded guilty today in the District of Columbia to federal charges related to a conspiracy to illegally export aircraft components and other items from the United States to entities in Iran via the Netherlands, the United Arab Emirates and Cyprus.

Laura Wang-Woodford, a U.S. citizen who served as a director of Monarch Aviation Pte Ltd., a Singapore company that imported and exported military and commercial aircraft components for more than 20 years, was sentenced today in federal court in Brooklyn to 46 months in prison for conspiring to violate the U.S. trade embargo by exporting controlled aircraft components to Iran.

Yi-Lan Chen, aka "Kevin Chen," 40, a Taiwan passport holder, was arrested on Feb. 3, 2010, on charges of illegally exporting commodities for Iran’s missile program.

Yi-Lan Chen, aka Kevin Chen, 40, a Taiwan passport holder, and his Taiwan corporation, Landstar Tech Company Limited, pleaded guilty today in Miami to charges of conspiring to illegally export dual-use commodities to Iran.

Zhen Zhou Wu aka Alex Wu, Yufeng Wei aka Annie Wei and Chitron Electronics Inc. (Chitron-US), were convicted of unlawfully exporting defense articles and Commerce controlled goods to China on numerous occasions between 2004 and 2007 and conspiring to violate U.S. export laws over a period of ten years.

Attorney General Eric Holder today announced the establishment of the Office of Tribal Justice as a separate component within the organizational structure of the Department of Justice.

Two Chinese nationals have been indicted by a federal grand jury in Alexandria, Va., for attempting to obtain radiation-hardened microchips, which are prohibited defense items used in the military and aerospace industry.

Seven individuals and five corporate entities based in the United States, France, the United Arab Emirates (U.A.E.) and Iran have been indicted in the Middle District of Georgia for their alleged roles in a conspiracy to illegally export military components for fighter jets and attack helicopters from the United States to Iran.

Five individuals and four of their companies have been indicted as part of a conspiracy to defraud the United States that allegedly caused thousands of radio frequency modules to be illegally exported from the United States to Iran, at least 16 of which were later found in unexploded improvised explosive devices (IEDs) in Iraq.

Michael Edward Todd, a U.S. national who is president of The Parts Guys LLC, a company in Port Orange, Fla., that maintains a warehouse at the Middle Georgia Municipal Airport in Macon, was sentenced this morning in federal court in the Middle District of Georgia.

From : Communities>>Regulatory Open Forum
This message was posted by a user wishing to remain anonymous For device-lead drug combination products, is there any difference in the quality (grade) of API used compared to a pure drug product? The cGMP guidance for combination products does not seem to specify, and since drug claims cannot be made on device-lead drug combination products, it was not clear what quality of drug is required. Thank you!

From : Communities>>Regulatory Open Forum
​I doubt FDA would have any willingness to change the requirements or expectations for a drug product based on whether it is in a strictly drug product versus in a combination product.  The fact also that there is not a published allowance for this is further evidence that FDA expects that the drug will meet the requirements as expected for drug products without providing any allowed changes or classes of changes.  Remember, FDA expects that drug products meet specific requirements.  Things like [More]

Easily create reusable, multistate button components for a slideshow project that features a self-generating, dynamic navigation. (6:45)

You won’t find as many styling solutions for React Native as you will for React JS. This stems from two simple realities:

1. React Native is a much smaller target for component libraries than traditional CSS frameworks. In other words, Bootstrap CSS can be used with any web framework, whereas component libraries for React Native only work with…you guessed it…React Native.
2. Customizing React Native styling isn’t the easiest thing in the world. Many apps demand custom styling, which makes component kits not too useful. In addition, it is challenging to customize each and every component, as the flexibility that you gain with traditional CSS on the web doesn’t carry over easily to component libraries.

With that said, here are a few options.

You won’t find as many styling solutions for React Native as you will for React JS. This stems from two simple realities:

1. React Native is a much smaller target for component libraries than traditional CSS frameworks. In other words, Bootstrap CSS can be used with any web framework, whereas component libraries for React Native only work with…you guessed it…React Native.
2. Customizing React Native styling isn’t the easiest thing in the world. Many apps demand custom styling, which makes component kits not too useful. In addition, it is challenging to customize each and every component, as the flexibility that you gain with traditional CSS on the web doesn’t carry over easily to component libraries.

With that said, here are a few options.

NativeBase - Essential cross-platform UI components for React Native

A huge collection of components, most of which look quite nice. That’s the plus side. The down side is that some of the components are somewhat buggy. No offense to the library authors, its just the state of the library - it needs a bit of work. For example, here’s an issue I opened a few days ago when I discovered the swipe deck component crashed when only a single data element was provided: DeskSwiper throws on single element lists · Issue #562 · GeekyAnts/NativeBase. The authors fixed it up awfully fast, but, hey, that’s a bug that seems like it could have been caught earlier.

React Native Elements - react-native-community/react-native-elements

This is my personal favorite. The styling is generally platform agnostic; it won’t look out of place using it on either Android or iOS. Each component has simple customization, the docs are solid, and it comes with a good set of icons. This is a no-brainer.

React Native Material Design - react-native-material-design/react-native-material-design

Another solid choice, but mostly only useful for Android. Again, its a bit unsettling to see material design - traditionally a stable of Android devices - on iOS. Besides that, the docs are still a work in progress, as evidenced by the lack of docs for nearly half of the components. Nonetheless, if you’re looking for a material design solution, this is better than nothing. It is also worth noting that the project looks generally unmaintained.

React Native Material Kit - xinthink/react-native-material-kit

Another material design solution, but much better maintained than React Native Material Design. This one has the added benefit of a nicer customization API for creating your own custom components - see the docs on this. It also has some more dynamic components like progress bars and sliders, which you may not see on other frameworks. Anything that helps save you time to build your app is always a solid benefit.

Do Your Own Styling!

If none of these choices float your boat, you can always learn how to style components from scratch yourself. I have a course on Udemy that will teach you how to make perfectly reusable components for your own projects. Check it out here: The Complete React Native and Redux Course - Udemy

The systolic and diastolic numbers in blood pressure reading predicted the risk of heart attack or stroke in a very large Kaiser Permanente study that

Microsoft’s Patch Tuesday for April released fixes for a couple of critical font-related vulnerabilities, like an earlier disclosed one found in Adobe Type Manager Library (atmfd.dll). It also featured patches for vulnerabilities in Microsoft SharePoint and Windows Components.

The post April Patch Tuesday: Fixes for Font-Related, Microsoft SharePoint, Windows Components Vulnerabilities appeared first on .

Company: P & I Management Consultants
Experience: 0 to 50
location: India
Ref: 24341090
Summary: Job Description: 1. Knowledge and ability to develop new products and process of hot forged Steel and Alloy components 2. Knowledge and ability to develop new products and process of sheet metal components including progressive and....

Exports of (bop) - Electrical Components in Canada increased to 484.70 CAD Million in March from 483 CAD Million in February of 2020. Exports of (bop) - Electrical Components in Canada averaged 314.42 CAD Million from 1988 until 2020, reaching an all time high of 720 CAD Million in February of 2014 and a record low of 68.10 CAD Million in January of 1988. This page includes a chart with historical data for Canada Exports of (bop) - Electrical Components.

Imports (Bop) - Prefabricated Buildings And Components in Canada decreased to 31.90 CAD Million in March from 39.80 CAD Million in February of 2020. Imports (Bop) - Prefabricated Buildings And Compon in Canada averaged 19.74 CAD Million from 1988 until 2020, reaching an all time high of 134.80 CAD Million in June of 1995 and a record low of 2.20 CAD Million in January of 1988. This page includes a chart with historical data for Canada Imports of (bop) - Prefabricated Buildings And Co.

Exports of Original Equipment Components CMLV in South Africa increased to 1.57 ZAR Million in March from 1.49 ZAR Million in February of 2020. Exports of Original Equipment Components CMLV in South Africa averaged 6.41 ZAR Million from 2014 until 2020, reaching an all time high of 21.42 ZAR Million in December of 2017 and a record low of 0.11 ZAR Million in January of 2017. South Africa accounts for Exports of Original Equipment Components using cumulative values for each year (CMLV). This page includes a chart with historical data for South Africa Exports of Original Equipment Components CMLV.

Imports of Original Equipment Components CMLV in South Africa increased to 28077.08 ZAR Million in March from 18339.06 ZAR Million in February of 2020. Imports of Original Equipment Components CMLV in South Africa averaged 49374.62 ZAR Million from 2014 until 2020, reaching an all time high of 107374.04 ZAR Million in December of 2019 and a record low of 6128.64 ZAR Million in January of 2015. South Africa accounts for Imports of Original Equipment Components using cumulative values for each year (CMLV). This page includes a chart with historical data for South Africa Imports of Original Equipment Components CMLV.

Imports of Automatic Data Proc. Eq. & Components in China increased to 4696200 USD THO in April from 4362100 USD THO in March of 2020. Imports of Automatic Data Proc. Eq. & Components in China averaged 1650802.16 USD THO from 1996 until 2020, reaching an all time high of 6685000 USD THO in February of 2020 and a record low of 16177 USD THO in May of 2014. This page includes a chart with historical data for China Imports of Automatic Data Proc. Eq. & Components.

600 overseas exhibitors to showcase their wares at the Component Show

कोरोना वायरस के संक्रमण से बचने के लिए पूरे देश में लॉकडाउन जारी है, लेकिन इस लॉकडाउन के चलते पूरे देश में ऑटो मोबाइल इंडस्ट्री की सप्लाई चेन बुरी तरह से प्रभावित हुई है, क्यों कि वाहन निर्माता कंपनियों ने सरकार के निर्देशानुसार उत्पादन बंद कर दिया था।

The Indian auto industry is slowly working its way to restart operations in India, after being shut down for over 40 days. Automobile companies are currently preparing to resume production in accordance with the government's guidelines for ensuring all safety and social distancing norms are followed.

Cham, Switzerland : Springer, [2019]

Interview with Michael E. Pichichero, MD, author of Combined Tetanus, Diphtheria, and 5-Component Pertussis Vaccine for Use in Adolescents and Adults, published in the June 22/29 issue of JAMA, the Journal of the American Medical Association. Summary Points: 1. Need: The combined tetanus-diphtheria 5-component pertussis vaccine is needed; There has been a 300% increase of pertussis among US adolescents in the last three years. 2. Safety: The combined tetanus-diphtheria 5-component pertussis vaccine is safe, as the reactions are the same as the tetanus vaccine. 3. Universal: On June 30, 2005, the American Academy of Pediatrics (ASAP), America Academy of Family Physicians (AFAR), and the Advisory Committee on Immunization Practices (ACID) all recommended the universal use of the combined tetanus-diphtheria 5-component pertussis vaccine or its competitor vaccine for adolescents.

Content marketing has gained much traction over the last 18 months and for good reasons. It is becoming an important part of any organizations marketing mix and can have an immediate impact on how companies are perceived, as well as their success online.

Content marketing also has an immediate impact on search.

complete article

Using CSS components is somewhat straightforward. We add the markup and give it the component’s class name and all is good. Where it gets trickier is when we try to nest components. And when they need to be tweaked based on the context. Where should the styles be defined? It’s a question I’ve been asking myself a few times and what this article is trying to explore.

Just to clarify before we start, with “CSS components”, I mean the small building blocks that get used to assemble a website or app. Like buttons, inputs, navs, headers etc. Some also call them modules or patterns. Also I’m using the SUIT naming convention in the examples below, but any other convention would be fine as well. And just a heads, there isn’t some awesome solution at the end that solves all the problems. It’s just me whining most of the time.

Ok, best is to go straight into it and look at an example. Let’s say we have a Header component where we would like to add a Button component inside.

<header class=“Header”>
  <button class=“Button”>Button</button>
</header>

Now because the Button is inside the Header, we want to make the Button a bit smaller than it would be on its own.

Here a few approaches how to do that:

Option 1 - Descendant selector

Maybe the most common way is to use a descendant selector to change the font-size whenever a Button is inside a Header.

.Header .Button {
  font-size: .75em;
}

This works great but the question is, where should this rule be added? We probably split our components into separate files, so is it in header.scss or in button.scss? In other words, should the Header know about what other components might get nested or should the Button know in what environment it will get placed?

But wait, the point of creating components is to separate them, make them modular. Each component should be kept isolated and shouldn’t know about other components. So we can make changes, rename or remove them without having to check if they might get used somewhere else.

Option 2 - Variations

Another way is to create variations. We add a .Button--small class that we can use whenever we would like the button to be smaller without having to worry about ancestors.

.Button--small {
  font-size: .75em;
}

<header class=“Header”>
  <button class=“Button Button--small”>Button</button>
</header>

This works great too, but could get out of hand quickly. What do you do if at some point you want the font-size to be .9em? Create yet another variation? Button--justALittleSmaller. As the project keeps growing, the number of variations will too. We will start to loose sight where they actually get used and we’re not sure anymore if we can change a variation or if it will have side effects in some other place. We could create “contextual” variations like Button--header or Button--footer, but then we’re back at the beginning and could just as well use “descendant selectors”.

Same goes for using states. .Button.is-small should only be used if there is a change in state and not to fit a certain context.

Option 3 - Adopted Child

I can’t remember where I read about this approach but somehow it stuck with me. I also forgot how it was called. So for now I’ll just call it “Adopted Child”.

Let’s switch it around and look at it from the Header’s perspective. What would we do if we wouldn’t know what the components are called that might get nested? But we know that we want to make them a bit smaller. Well, we probably would create a generic .Header-item class and use it like this:

.Header-item {
  font-size: .75em;
}

<header class=“Header”>
  <div class=“Header-item”></div>
</header>

Ok, that gets us a bit closer. Now, it’s probably strange saying it like that when talking about CSS, but what would we do if we don’t want to create an own child, but still have one. Right, we could adopt one. In our example we adopt a Button component as our own child. We didn’t create it, but now we can tweak.. erm.. I mean “raise” it like it’s our own:

// born in button.scss
.Button {
  font-size: 1em;
}

// raised in header.css
.Header .Header-item {
  font-size: .75em;
}

<header class=“Header”>
  <button class=“Header-item Button”>Button</button>
</header>

It is a bit uncommon that the same HTML element shares classes from two different components. And it’s not without any risks. More about them later. But I really like this approach because it keeps the components independent without having to know about each other.

Another nice thing is that if we want to add other components to the Header that also need the same adjustments, we can reuse the same Header-item class, like for example on a text Input.

<header class=“Header”>
	<input class=“Header-item Input”>
  <button class=“Header-item Button”>Button</button>
</header>

Ok, about those risks. Well, depending on what properties we wanna change, it might not always be ideal. For example, because the Button already had font-size defined, we had to increase specificity by using .Header .Header-item. But that would also override variations like .Button--small. That might be how we want it, but there are also situations where we’d like the variation to always be “stronger”. An example would be when changing colors. When the color of Buttons should be different inside a Header, but not when its a variation, like .Button—primary. Yeah, we could take a look inside button.scss or our style-guide, but remember our goal.. we actually don’t want to make decisions by looking how other components are made.

So, as a general rule, don’t use “adopted children” for any properties that are theme related and only where you can be sure that you want to override them all the time. Like for layout/size related properties or adjusting the position.

More options?

There are some more ways to do contextual styling that came to mind. I’ll just mention them briefly for completeness, but think the 3 above are better suited.

Option 4 - We could use a preprocessor to extend an existing component. In our example it would be a clone of the Button with some tweaks added and used as a new child component .Header-button. Now we only rely that the Button exists in the source, but don’t have to worry about other contexts. Downside is inflating our CSS output. As well as having to remember lots of new child component classes.

Option 5 - We could create a utility class like .u-small. It’s similar to variations, but not scoped to a single component and could be used for other components as well. And for that reason it becomes very risky to ever change later.

Option 6 - And of course, we could use inline styles. But I would leave that to JavaScript only.

So after all that, which is best? I’m afraid there isn’t a clear winner. It would be nice to keep it consistent with a single approach throughout the entire project, but I guess we just have to decide on a per case basis:

1. Descendant selectors if we can expect that components don’t change much. Like when using a UI Kit or library.
2. Variations if it makes sense that a component has different versions that get reused anyways, and not just for a specific context.
3. Adopted Child for layout, sizing, positioning or where we are sure to always want to override a property. Also for changing multiple child components at once.
4. Extending when we truly want the components to be separated and don’t mind inflating the CSS output.
5. Utilities for very specific things, that once the class is defined, it will never change, like clearing floats.
6. Inline styles if it needs to be dynamically added with JavaScript.

As said at the beginning, I haven’t found a “fits all” solution and maybe the conclusion is: Try to keep contextual styling to a minimum.

Updates

The “Adopted Child” approach is called “Mixes” in BEM. Here some more infos.

SUIT also recommends using “Adopted Child/Mixes”. But also another option:

Option 7 - Adding a wrapper element. It’s the <div class="Excerpt-wrapButton"> in that example. I think it works great in most cases. But for example when using Flexbox, because it has this parent/child relationship, adding an extra wrapper in between would break it. And then you might still need to set the width of the wrapped component to 100% or so. Anyways, this is a great addition. Thanks Pablo in the comments.

Option 8 - Single Purpose Classes. It’s where every class has only a single property. It’s somewhere between utilities (Option 5) and inline styles (Option 6). Atomic CSS and Tachyons use this approach. I haven’t used them on a real project, but just from looking at it, the concerns are similar to the ones from utilities. If you want to change the value in a SP class, it seems unpredictable. Because in another place (where that same class is used), you might want to keep the current value. So you would have to first check if the change has any unwanted effects somewhere else.

Online Resource