The 10 most-cited articles in Journal of Bacteriology, 2022

Oral commensal streptococci are primary colonizers of the oral cavity. These streptococci produce many adhesins, metabolites, and antimicrobials that modulate microbial succession and diversity within the oral cavity. Often, oral commensal streptococci antagonize cariogenic and periodontal pathogens such as Streptococcus mutans and Porphyromonas gingivalis, respectively. Mechanisms of antagonism are varied and range from the generation of hydrogen peroxide, competitive metabolite scavenging, the generation of reactive nitrogen intermediates, and bacteriocin production. Furthermore, several oral commensal streptococci have been shown to alter the host immune response at steady state and in response to oral pathogens. Collectively, these features highlight the remarkable ability of oral commensal streptococci to regulate the structure and function of the oral microbiome. In this review, we discuss mechanisms used by oral commensal streptococci to interact with diverse oral pathogens, both physically and through the production of antimicrobials. Finally, we conclude by exploring the…

ABSTRACT The current classification of the phylum Firmicutes (new name, Bacillota ) features eight distinct classes, six of which include known spore-forming bacteria. In Bacillus subtilis , sporulation involves up to 500 genes, many of which do not have orthologs in other bacilli and/or clostridia. Previous studies identified about 60 sporulation genes of B. subtilis that were shared by all spore-forming members of the Firmicutes. These genes are referred to as the sporulation core or signature although many of these are found also in genomes of non-spore-formers. Using an expanded set of 180 firmicute genomes from 160 genera, including 76 spore-forming species, we investigated the conservation of the sporulation genes, in particular, seeking to identify lineages that lack some of the genes from the conserved sporulation core. The results of this analysis confirmed that many small acid-soluble spore proteins (SASPs), spore coat proteins, and germination proteins, which were previously characterized in bacilli, are missing in spore-forming members of Clostridia and other classes of…

Escherichia coli is likely the most studied organism and was instrumental in developing many fundamental concepts in biology. But why E. coli? In the 1940s, E. coli was well suited for the biochemical and genetic research that blended to become the seminal field of biochemical genetics and led to the realization that processes already known to occur in complex organisms were conserved in bacteria. This now-obvious concept, combined with the advantages offered by its easy cultivation, ultimately drove many researchers to shift from the complexity of eukaryotic models to the simpler bacterial system, which eventually led to the development of molecular biology. As knowledge and experimental tools amassed, a positive-feedback loop fixed the central role of E. coli in research. However, given the vast diversity among bacteria and even among E. coli strains, it was by many fortuitous events that E. coli rose to the top as an experimental model. Here, we share how serendipity and its own biology selected E. coli as the flagship bacterium of molecular biology.

The DNA-binding protein from starved cells, Dps, is a universally conserved prokaryotic ferritin that, in many species, also binds DNA. Dps homologs have been identified in the vast majority of bacterial species and several archaea. Dps also may play a role in the global regulation of gene expression, likely through chromatin reorganization. Dps has been shown to use both its ferritin and DNA-binding functions to respond to a variety of environmental pressures, including oxidative stress. One mechanism that allows Dps to achieve this is through a global nucleoid restructuring event during stationary phase, resulting in a compact, hexacrystalline nucleoprotein complex called the biocrystal that occludes damaging agents from DNA. Due to its small size, hollow spherical structure, and high stability, Dps is being developed for applications in biotechnology.

The opportunistic pathogen Pseudomonas aeruginosa produces a complex biofilm matrix comprised of exopolysaccharides (EPSs), nucleic acids, and proteins. P. aeruginosa biofilm formation canonically depends on a variable combination of the exopolysaccharides Psl and Pel and the matrix protein CdrA. We demonstrate that mucoid P. aeruginosa, which overproduces the EPS alginate, possesses an entirely alternate and calcium-dependent method of biofilm formation. These mucoid biofilm structures do not require Psl, Pel, or CdrA, and they display a unique organization of individually suspended cells similar to bacterial aggregates observed in cystic fibrosis airways. Furthermore, calcium-gelled mucoid biofilms impede the penetration and killing action of the antibiotic tobramycin, illustrating their potential clinical significance. Our findings highlight the compositional and structural variety of P. aeruginosa biofilm aggregates.

trials, lactobacilli counteract and inhibit various virulence factors that favor pathogens, including the production of toxins, biofilm formation, host cell adhesion and invasion, and downregulation of virulence genes linked to quorum sensing. The aim of this review is to summarize current studies on the inhibition of pathogen virulence by lactobacilli, an important microbial group well known in the industrial and medical fields for their technological and probiotic properties that benefit human hosts with the potential to provide an important aid in the fight against pathogens besides use of the current therapies. Further research could lead to the identification of new strains that, in addition to alleviating adverse effects, could improve the efficacy of antibiotic therapies or play an important preventive role by reducing the onset of pathogen infections if regularly taken.

Many infections are polymicrobial and biofilm-associated in nature. Iron is essential for many metabolic processes and plays an important role in controlling infections, where the host restricts iron as a defense mechanism against invading pathogens. However, polymicrobial interactions between pathogens are underexplored under iron-restricted conditions. Here, we explore the polymicrobial interactions between commonly coisolated E. faecalis and P. aeruginosa within biofilms. We find that E. faecalis modulates the microenvironment by exporting lactic acid which further chelates already limited iron and also lowers the environmental pH to antagonize P. aeruginosa growth under iron-restricted conditions. Our findings provide insights into polymicrobial interactions between bacteria and how manipulating the microenvironment can be taken advantage of to better control infections.

Abstract The class A penicillin-binding proteins (aPBPs), PBP1A and PBP1B, are major peptidoglycan synthases that synthesize more than half of the peptidoglycan per generation in Escherichia coli . Whereas aPBPs have distinct roles in peptidoglycan biosynthesis during growth (i.e., elongation and division), they are semi-redundant; disruption of either is rescued by the other to maintain envelope homeostasis and promote proper growth. Acinetobacter baumannii is a nosocomial pathogen that demonstrated a high propensity to overcome antimicrobial treatment. A. baumannii encodes both PBP1A and PBP1B (encoded by mrcA and mrcB , respectively), but only mrcA deletion decreased fitness and contributed to colistin resistance through inactivation of lipooligosaccharide biosynthesis, indicating that PBP1B was not functionally redundant with PBP1A activity. While previous studies suggested a distinct role for PBP1A in division, it was unknown if its role in septal peptidoglycan biosynthesis was direct. Here, we show that A. baumannii PBP1A has a direct role in division through interactions with…

Most microbes in the biosphere are attached to surfaces, where they experience mechanical forces due to hydrodynamic flow and cell-to-substratum interactions. These forces likely serve as mechanical cues that influence bacterial physiology and eventually drive environmental adaptation and fitness. Mechanosensors are cellular components capable of sensing a mechanical input and serve as part of a larger system for sensing and transducing mechanical signals. Two cellular components in bacteria that have emerged as candidate mechanosensors are the type IV pili (TFP) and the flagellum. Current models posit that bacteria transmit and convert TFP- and/or flagellum-dependent mechanical force inputs into biochemical signals, including cAMP and c-di-GMP, to drive surface adaptation. Here, we discuss the impact of force-induced changes on the structure and function of two eukaryotic proteins, titin and the human von Willebrand factor (vWF), and these proteins' relevance to bacteria. Given the wealth of understanding about these eukaryotic mechanosensors, we can use them as a framework to…

(thiamin) is an essential nutrient for cellular metabolism. Microorganisms that are unable to synthesize thiamin either fully or in part exogenously obtain it from their environment or via exchanges with other microbial members in their community. In this study, we created synthetic microbial cocultures that rely on sharing thiamin and its biosynthesis intermediates and observed that some of them are preferentially exchanged. We also observed that the coculture composition is dictated by the production and/or availability of thiamin and its intermediates. Our studies with synthetic cocultures provide the molecular basis for understanding thiamin sharing among microorganisms and lay out broad guidelines for setting up synthetic microbial cocultures by using the exchange of an essential metabolite as their foundation.