A biofilm is an organized, resilient group of microbes in which individual cells acquire properties, such as drug resistance, that are distinct from those observed in suspension cultures. Here, we ...describe and analyze the transcriptional network controlling biofilm formation in the pathogenic yeast Candida albicans, whose biofilms are a major source of medical device-associated infections. We have combined genetic screens, genome-wide approaches, and two in vivo animal models to describe a master circuit controlling biofilm formation, composed of six transcription regulators that form a tightly woven network with ∼1,000 target genes. Evolutionary analysis indicates that the biofilm network has rapidly evolved: genes in the biofilm circuit are significantly weighted toward genes that arose relatively recently with ancient genes being underrepresented. This circuit provides a framework for understanding many aspects of biofilm formation by C. albicans in a mammalian host. It also provides insights into how complex cell behaviors can arise from the evolution of transcription circuits.
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► Candida biofilms are controlled by a network of six master transcription regulators ► The biofilm network is highly interconnected and contains > 1,000 target genes ► Computational analysis indicates that the biofilm network has rapidly evolved ► The network interconnectedness provides clues as to how complex circuits evolve
Biofilms of the pathogenic fungus C. albicans coat medical devices and contribute to drug-resistant infections. Revealing the transcriptional circuit responsible for biofilm formation provides insight into how complex cell behaviors arise from the evolution of regulatory circuits.
Virtually nothing in nature is uniform. Observed at the right scale, most entities are clustered rather than evenly distributed, spatially and temporally, and this applies across domains from the ...distribution of matter in the universe, to habitats across the Earth's surface, and to energy in the landscape. Patchiness means organisms cannot carve out even territories. Instead, their shape and size depends on the dispersion of materials needed for survival and reproduction. This fundamental feature of life is intrinsically understood in ecology, for example, in the ideal free distribution and optimal foraging theory, and is represented in the anatomy as well as behaviour of organisms via the structures and strategies for moving, finding and capturing these patchy resources. But perhaps most striking of all is the role of patchiness in facilitating the formation of social groups – of societies. The resource dispersion hypothesis (RDH) suggests that where resources are dispersed and rich enough, multiple individuals can collapse into groups that share the same space at little cost to each other. Cooperation may be absent, but sociality is favoured nevertheless. Thirty years after the origin of the hypothesis, we review the accumulating models, critiques, evidence and experiments, concluding that RDH is a pervasive feature of animal spacing patterns across a wide range of species, taxonomic groups and ecosystems. In the spirit of the original objective of the Huxley Reviews to ‘suggest and inspire research that will improve our knowledge in the future’, we also take the opportunity to consider wider implications of the RDH. If we live and evolved on a patchwork planet, then we should expect broader effects. Indeed, we suggest that the RDH has played an important role in the evolution of cooperation, biodiversity, behaviour and, not least, in the social organization of humans in our evolutionary past and today.
The genus Acidithiobacillus includes three species that conserve energy from the oxidation of ferrous iron, as well as reduced sulfur, to support their growth. Previous work, based on multi-locus ...sequence analysis, identified a fourth group of iron- and sulfur-oxidizing acidithiobacilli as a potential distinct species. Eleven strains of 'Group IV' acidithiobacilli, isolated from different global locations, have been studied. These were all shown to be obligate chemolithotrophs, growing aerobically by coupling the oxidation of ferrous iron or reduced sulfur (but not hydrogen) to molecular oxygen, or anaerobically by the oxidation of reduced sulfur coupled to ferric iron reduction. All strains were mesophilic, although some were also psychrotolerant. Strain variation was also noted in terms of tolerance to extremely low pH and to elevated concentrations of transition metals. One strain was noted to display far greater tolerance to chloride than reported for other iron-oxidizing acidithiobacilli. All of the strains were able to catalyse the oxidative dissolution of pyrite and, on the basis of some of the combined traits of some of the strains examined, it is proposed that these may have niche roles in commercial mineral bioprocessing operations, such as for low temperature bioleaching of polysulfide ores in brackish waters. The name Acidithiobacillus ferriphilus sp. nov. is proposed to accommodate the strains described, with the type strain being M20T ( = DSM 100412T = JCM 30830T).
We explore the connection between the UV luminosity functions (LFs) of high-z galaxies and the distribution of stellar masses and star formation histories (SFHs) in their host dark matter halos. We ...provide a baseline for a redshift-independent star formation efficiency model to which observations and models can be compared. Our model assigns a star formation rate (SFR) to each dark matter halo based on the growth rate of the halo and a redshift-independent star formation efficiency. The dark matter halo accretion rate is obtained from a high-resolution N-body simulation in order to capture the stochasticity in accretion histories and to obtain spatial information for the distribution of galaxies. The halo mass dependence of the star formation efficiency is calibrated at z = 4 by requiring a match to the observed UV LF at this redshift. The model then correctly predicts the observed UV LF at z = 5-10. We present predictions for the UV luminosity and stellar mass functions, JWST number counts, and SFHs. In particular, we find a stellar-to-halo mass relation at z = 4-10 that scales with halo mass at Mh < 1011 M as M ∝ Mh2, with a normalization that is higher than the relation inferred at z = 0. The average SFRs increase as a function of time to z = 4, although there is significant scatter around the average: about 6% of the z = 4 galaxies show no significant mass growth. Using these SFHs, we present redshift-dependent UV-to-SFR conversion factors, mass return fractions, and mass-to-light ratios for different initial mass functions and metallicities, finding that current estimates of the cosmic SFR density at z ∼ 10 may be overestimated by ∼0.1-0.2 dex.
Candida albicans is among the most prevalent fungal species of the human microbiota and asymptomatically colonizes healthy individuals. However, it is also an opportunistic pathogen that can cause ...severe, and often fatal, bloodstream infections. The medical impact of C. albicans typically depends on its ability to form biofilms, which are closely packed communities of cells that attach to surfaces, such as tissues and implanted medical devices. In this Review, we provide an overview of the processes involved in the formation of C. albicans biofilms and discuss the core transcriptional network that regulates biofilm development. We also consider some of the advantages that biofilms provide to C. albicans in comparison with planktonic growth and explore polymicrobial biofilms that are formed by C. albicans and certain bacterial species.
Summary
Extremely acidic, sulfur‐rich environments can be natural, such as solfatara fields in geothermal and volcanic areas, or anthropogenic, such as acid mine drainage waters. Many species of ...acidophilic bacteria and archaea are known to be involved in redox transformations of sulfur, using elemental sulfur and inorganic sulfur compounds as electron donors or acceptors in reactions involving between one and eight electrons. This minireview describes the nature and origins of acidic, sulfur‐rich environments, the biodiversity of sulfur‐metabolizing acidophiles, and how sulfur is metabolized and assimilated by acidophiles under aerobic and anaerobic conditions. Finally, existing and developing technologies that harness the abilities of sulfur‐oxidizing and sulfate‐reducing acidophiles to extract and capture metals, and to remediate sulfur‐polluted waste waters are outlined.
Acidithiobacillus ferrooxidans Quatrini, Raquel; Johnson, D. Barrie
Trends in microbiology (Regular ed.),
March 2019, 2019-03-00, 20190301, Letnik:
27, Številka:
3
Journal Article
Recenzirano
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Acidithiobacillus ferrooxidans is by far the most widely studied of all extremely acidophilic prokaryotes. While it is found in many types of natural low-pH environments in a variety ...of geoclimatic contexts, it has been more widely cited in anthropogenic (mostly mine-impacted) environments. It is responsible for accelerating the oxidative dissolution of sulfide minerals, causing the generation of polluting acidic metal-rich drainage waters but also facilitating the recovery of base and precious metals from mineral leachates. It can colonize barren mineral landscapes, is a driver of ecological successions in acidic biotopes, and is an important model organism in astrobiology. It catalyses the dissimilatory oxidation of iron, sulfur, and hydrogen, and the reduction of iron and sulfur, and has a major impact in the geochemical cycling of these elements in low-pH environments. This infographic summarizes the fundamental phylogeny, physiology and genomic features of this extremophile.
The binding of transcription regulators to cis-regulatory sequences is a key step through which all cells regulate expression of their genes. Due to gains and losses of cis-regulatory sequences and ...changes in the transcription regulators themselves, the binding connections between regulators and their target genes rapidly change over evolutionary time and constitute a major source of biological novelty. This review covers recent work, carried out in a wide range of species, that addresses the overall extent of these evolutionary changes, their consequences, and some of the molecular mechanisms that lie behind them.
We draw on eight different lab and field samples to delineate the effects of expressed humility on several important organizational outcomes, including performance, satisfaction, learning goal ...orientation, engagement, and turnover. We first review several literatures to define the construct of expressed humility, discuss its implications in social interactions, and distinguish expressed humility from related constructs. Using five different samples, Study 1 develops and validates an observer-report measure of expressed humility. Study 2 examines the strength of expressed humility predictions of individual performance and contextual performance (i.e., quality of team member contribution) relative to conscientiousness, global self-efficacy, and general mental ability. This study also reveals that with regard to individual performance, expressed humility may compensate for lower general mental ability. Study 3 reports insights from a large field sample that examines the relationship between leader-expressed humility and employee retention as mediated by job satisfaction and employee engagement as mediated by team learning orientation. We conclude with recommendations for future research.
The production of fully functional insulin-secreting cells to treat diabetes is a major goal of regenerative medicine. In this article, I review progress towards this goal over the last 15 years from ...the perspective of a beta cell biologist. I describe the current state-of-the-art, and speculate on the general approaches that will be required to identify and achieve our ultimate goal of producing functional beta cells. The need for deeper phenotyping of heterogeneous cultures of stem cell derived islet-like cells in parallel with a better understanding of the heterogeneity of the target cell type(s) is emphasised. This deep phenotyping should include high-throughput single-cell analysis, as well as comprehensive ’omics technologies to provide unbiased characterisation of cell products and human beta cells. There are justified calls for more detailed and well-powered studies of primary human pancreatic beta cell physiology, and I propose online databases of standardised human beta cell responses to physiological stimuli, including both functional and metabolomic/proteomic/transcriptomic profiles. With a concerted, community-wide effort, including both basic and applied scientists, beta cell replacement will become a clinical reality for patients with diabetes.
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