Biology subjects

Arjes, H. A.

Publications and source records attributed to Arjes, H. A..

5 recordsLinked to original sources

bioRxiv2026

Systematic discovery of a topical bacterial consortium that targets Staphylococcus aureus to treat atopic dermatitis

Atopic dermatitis (AD) flares are frequently accompanied by Staphylococcus aureus overgrowth and activation of quorum sensing-regulated virulence pathways that amplify inflammation and barrier dysfunction. Because commensal members of the skin microbiome can inhibit S. aureus colonization and virulence, we hypothesized that a consortium sourced from healthy human skin could therapeutically target S. aureus and ameliorate AD. We curated 180 skin-derived bacterial strains and used kChip, an ultrahigh-throughput coculture platform, to profile S. aureus physiological response to over four million combinations consisting of two, three, or seven cocultured strains. This screening identified Ensemble No.2 (ENS-002), a three-strain consortium that strongly suppressed S. aureus growth and virulence in follow-up microtiter assays and a Reconstructed Human Epidermis S. aureus Activity (RHESA) model. ENS-002 is now undergoing development as a topical live biotherapeutic product (LBP) treatment for AD.

microbiology↗

bioRxiv2022

Fatty acid synthesis knockdown promotes biofilm wrinkling and inhibits sporulation in Bacillus subtilis

Many bacterial species typically live in complex three-dimensional biofilms, yet little is known about systematic changes to gene function between non-biofilm and biofilm lifestyles. Here, we created a CRISPRi library of knockdown strains covering all known essential genes in the biofilm-forming Bacillus subtilis strain 3610. We show that gene essentiality is largely conserved between liquid and surface growth and between two media. We developed an image analysis algorithm to quantify biofilm colony wrinkling, which identified strains with high or low levels of wrinkling that were uncorrelated with extracellular matrix gene expression. We also designed a high-throughput screen for sensitive quantification of sporulation efficiency and performed the first screens of sporulation during essential gene knockdown. We found that all basal knockdowns of essential genes were competent for sporulation in a sporulation-inducing medium, but certain strains exhibited reduced sporulation efficiency in LB, a medium with generally lower levels of sporulation. Knockdown of fatty acid synthesis increased wrinkling and inhibited sporulation. These results highlight the importance of essential genes in biofilm structure and sporulation/germination and suggest a previously unappreciated and multifaceted role for fatty acid synthesis in bacterial lifestyles and developmental processes. Abstract ImportanceFor many bacteria, life typically involves growth in dense, three-dimensional communities called biofilms that contain cells with differentiated roles and are held together by extracellular matrix. To examine how gene function varies between non-biofilm and biofilm growth, we created a comprehensive library of strains using CRISPRi to knockdown expression of each essential gene in the model species Bacillus subtilis 3610, which can develop into a wrinkled biofilm structure or a spore capable of surviving harsh environments. This library enabled us to determine when gene essentiality depends on growth conditions. We also developed high-throughput assays and computational algorithms to identify essential genes involved in biofilm wrinkling and sporulation. Knockdown of fatty acid synthesis increased the density of wrinkles, and also inhibited sporulation in a medium with generally lower sporulation levels. These findings indicate that essential processes such as fatty acid synthesis can play important and multifaceted roles in bacterial development.

microbiology↗

bioRxiv2021

Construction and characterization of a genome-scale ordered mutant collection of Bacteroides thetaiotaomicron

Genomic analyses have revealed how the gut microbiota impacts human health. However, knowledge about the physiology of most gut commensals is largely lacking. Here, we sorted cells from a pooled library to construct an ordered collection of transposon-insertion mutants in the model commensal Bacteroides thetaiotaomicron. We applied a pooling strategy with barcode sequencing to locate mutants and created a condensed collection with single insertions in 2,565 genes. This effort enabled the development of an accurate model for progenitor-collection assembly, which identified strain-abundance biases and multi-insertion strains as important factors that limit coverage. To demonstrate the potential for phenotypic screening, we analyzed growth dynamics and morphology of the condensed collection and identified growth defects and altered cell shape in the sphingolipid-synthesis gene BT0870 and the thiamine scavenging gene BT2397. Analyses of this collection and utilization of the platform described herein to construct future ordered libraries will increase understanding of gut commensal physiology and colonization strategies.

microbiology↗

bioRxiv2020

Three-dimensional biofilm growth supports a mutualism involving matrix and nutrient sharing

Life in a three-dimensional structure such as a biofilm is typical for many bacteria, yet little is known about how strains with different genotypes interact in this context. Here, to systematically explore gene knockdowns across various three-dimensional contexts, we created arrayed libraries of essential-gene CRISPRi knockdowns in the model biofilm-forming bacterium Bacillus subtilis and measured competitive fitness during colony co-culture with a wild type-like parent on different media and at different knockdown levels. Partial knockdown led to a wide range of fitness phenotypes, with targeting of translation-related genes often leading to lower growth rates and rapid out-competition by the parent. Several knockdowns competed differentially in biofilms versus non-biofilm colonies, in some cases due to lack of a particular nutrient in one medium. Cells depleted for the alanine racemase AlrA died in monoculture, but co-cultures survived via nutrient sharing in a biofilm but not in liquid. This rescue was enhanced in biofilm co-culture with a parent unable to produce extracellular matrix, due to a mutualism involving nutrient and matrix sharing. Including alrA, we identified several examples of mutualism involving matrix sharing that occurred in a three-dimensional biofilm colony but not when growth was constrained to two dimensions. These findings demonstrate that growth in a three-dimensional biofilm can promote genetic diversity through sharing of secreted factors, and illustrate the role of matrix production in determining trajectories for biofilm evolution that may be relevant to pathogens and other environmental bacteria.

microbiology↗

bioRxiv2019

Biosurfactant production maintains viability in anoxic conditions by depolarizing the membrane in Bacillus subtilis

The presence or absence of oxygen in the environment is a strong effector of cellular metabolism and physiology. Like many eukaryotes and some bacteria, Bacillus subtilis is an obligate aerobe that primarily utilizes oxygen during respiration to generate ATP. Despite the importance of oxygen for B. subtilis survival, we know little about how oxygen is consumed during growth and how populations respond to shifts in oxygen availability. Here, we find that when oxygen was depleted from stationary phase cultures [~]90% of B. subtilis 3610 cells died and lysed due to autolysin activity; the remaining cells maintained colony-forming ability. Interestingly, the domesticated 168 strain maintained a higher optical density than 3610 during oxygen depletion due to the formation of cell-wall-less protoplasts, but the remaining, rod-shaped cells were >100-fold less viable than 3610. We discovered that the higher viability in 3610 was due to its ability to produce the antibacterial compound surfactin, as surfactin addition rescued 168 viability and also increased yield in aerobic growth. We further demonstrate that surfactin strongly depolarizes the B. subtilis membrane, and that other known membrane-potential disruptors restore viability to 168. These findings highlight the importance of surfactin for survival during oxygen-depleted conditions and demonstrate that antimicrobials normally considered harmful can instead benefit cells in stressful conditions when the terminal electron acceptor in respiration is limiting.

microbiology↗