Alterations in cell arrangements of group B streptococcus due to virulence factor expression can bias estimates of bacterial populations based on colony count measures.

Group B streptococcus (GBS) is a chain-forming commensal bacterium and opportunistic pathogen that resides in the gastrointestinal and genitourinary tract of healthy adults. GBS can cause various infections and related complications in pregnant and nonpregnant women, adults, and newborns. Investigations of the mechanisms by which GBS causes disease pathogenesis often utilize colony count assays to estimate bacterial population size in experimental models. In other streptococci, such as group A streptococcus and pneumococcus, variation in the chain length of the bacteria that can occur naturally or due to mutation can affect facets of pathogenesis, such as adherence to or colonization of a host. No studies have reported a relationship between GBS chain length and pathogenicity. Here, we used GBS strain 874391 and several derivative strains displaying longer chain-forming phenotypes (874391pgapC, 874391ΔcovR, 874391Δstp1) to assess the impact of chain length on bacterial population estimates based on the colony-forming unit (c.f.u.) assay. Disruption of GBS chains via bead beating or sonication in conjunction with fluorescence microscopy was used to compare chaining phenotypes pre- and post-disruption to detect long- and short-chain forms, respectively. We used a murine model of GBS colonization of the female reproductive tract to assess whether chaining may affect bacterial colonization dynamics in the host during chronic infection in vivo. Overall, we found that GBS exhibiting long-chain form can significantly affect population size estimates based on the colony count assay. Additionally, we found that the length of chaining of GBS can affect virulence in the reproductive tract colonization model. Collectively, these findings have implications for studies of GBS that utilize colony count assays to measure GBS populations and establish that chain length can affect infection dynamics and disease pathogenesis for this important opportunistic pathogen.

Fluorescent carbon dots for labeling of bacteria: mechanism and prospects-a review.

The search for bacteria-labeling agents that are more efficient and less toxic compared to existing staining dyes is ongoing. Fluorescent quantum dots and carbon dots (CDs) have been extensively researched for various bioimaging applications. Priority is given to CDs due to several advantages, including lower toxicity, versatility in tuning their properties, and better photostability compared to metal-based quantum dots. Although significant progress is still needed to replace existing dyes with CDs for bacteria labeling, they offer promising potential for further improvement in efficiency. Surface charges and functional groups have been reported as decisive factors for bacterial discrimination and live/dead assays; however, a complete guideline for preparing CDs with optimum properties for efficient staining and predicting their labeling performance is lacking. In this review, we discuss the application of fluorescent CDs for bacterial labeling and the underlying mechanisms and principles. We primarily focus on the application and mechanism of CDs for Gram differentiation, live imaging, live/dead bacteria differentiation, bacterial viability testing, biofilm imaging, and the challenges associated with application of CDs. Based on proposed mechanisms of bacterial labeling and ambiguous results reported, we provide our view and guidelines for the researchers in this field to overcome the challenges associated with bacteria labeling using fluorescent CDs.

pyPGCF: A Python Software for Phylogenomic Analysis, Species Demarcation, Identification of Core, and Fingerprint Proteins of Bacterial Genomes That Are Important for Plants.

This computational protocol describes how to use pyPGCF, a python software package that runs in the linux environment, in order to analyze bacterial genomes and perform: (i) phylogenomic analysis, (ii) species demarcation, (iii) identification of the core proteins of a bacterial genus and its individual species, (iv) identification of species-specific fingerprint proteins that are found in all strains of a species and, at the same time, are absent from all other species of the genus, (v) functional annotation of the core and fingerprint proteins with eggNOG, and (vi) identification of secondary metabolite biosynthetic gene clusters (smBGCs) with antiSMASH. This software has already been implemented to analyze bacterial genera and species that are important for plants (e.g., Pseudomonas, Bacillus, Streptomyces). In addition, we provide a test dataset and example commands showing how to analyze 165 genomes from 55 species of the genus Bacillus. The main advantages of pyPGCF are that: (i) it uses adjustable orthology cut-offs, (ii) it identifies species-specific fingerprints, and (iii) its computational cost scales linearly with the number of genomes being analyzed. Therefore, pyPGCF is able to deal with a very large number of bacterial genomes, in reasonable timescales, using widely available levels of computing power.

Description of postoperative complications and bacterial contamination of wound soaker catheters used to administer postoperative local analgesia after mastectomy in 11 dogs: case series.

Mastectomy is a common and painful procedure in dogs. Wound soaker catheters (WSC) are frequently used to reduce postoperative pain, including pain after mastectomy. The objectives of this case series were to describe the use of WSC for owner administration of postoperative local analgesia in dogs with mammary tumors treated surgically, to identify complications associated with WSC and to determine the frequency of bacterial colonization of the catheters. Twelve WSC were placed in 11 dogs during mastectomy surgery, left in place for three days, protected by a dressing and successfully managed by owners at home. No postoperative antibiotics were administered. No complications were identified in any cases. No bacterial growth was identified on bacteriological analysis of the twelve WSC. These results suggest that the use of WSC is a safe alternative for postoperative analgesia administration following mastectomy in dogs. Future studies comparing dogs with or without WSC with a larger number of dogs are needed to further evaluate efficacy and complications.

Gyrase and Topoisomerase IV: Recycling Old Targets for New Antibacterials to Combat Fluoroquinolone Resistance.

Beyond their requisite functions in many critical DNA processes, the bacterial type II topoisomerases, gyrase and topoisomerase IV, are the targets of fluoroquinolone antibacterials. These drugs act by stabilizing gyrase/topoisomerase IV-generated DNA strand breaks and by robbing the cell of the catalytic activities of these essential enzymes. Since their clinical approval in the mid-1980s, fluoroquinolones have been used to treat a broad spectrum of infectious diseases and are listed among the five "highest priority" critically important antimicrobial classes by the World Health Organization. Unfortunately, the widespread use of fluoroquinolones has been accompanied by a rise in target-mediated resistance caused by specific mutations in gyrase and topoisomerase IV, which has curtailed the medical efficacy of this drug class. As a result, efforts are underway to identify novel antibacterials that target the bacterial type II topoisomerases. Several new classes of gyrase/topoisomerase IV-targeted antibacterials have emerged, including novel bacterial topoisomerase inhibitors, Mycobacterium tuberculosis gyrase inhibitors, triazaacenaphthylenes, spiropyrimidinetriones, and thiophenes. Phase III clinical trials that utilized two members of these classes, gepotidacin (triazaacenaphthylene) and zoliflodacin (spiropyrimidinetrione), have been completed with positive outcomes, underscoring the potential of these compounds to become the first new classes of antibacterials introduced into the clinic in decades. Because gyrase and topoisomerase IV are validated targets for established and emerging antibacterials, this review will describe the catalytic mechanism and cellular activities of the bacterial type II topoisomerases, their interactions with fluoroquinolones, the mechanism of target-mediated fluoroquinolone resistance, and the actions of novel antibacterials against wild-type and fluoroquinolone-resistant gyrase and topoisomerase IV.

Communication leads to bacterial heterogeneous adaptation to changing conditions in partial nitrification reactor.

Recently, it is reported that bacterial communication coordinates the whole consortia to jointly resist the adverse environments. Here, we found the bacterial communication inevitably distinguished bacterial adaptation among different species in partial nitrification reactor under decreasing temperatures. We operated a partial nitrification reactor under temperature gradient from 30 °C to 5 °C and found the promotion of bacterial communication on adaptation of ammonia-oxidizing bacteria (AOB) was greater than that of nitrite-oxidizing bacteria (NOB). Signal pathways with single-component sensing protein in AOB can regulate more genes involved in bacterial adaptation than that with two-component sensing protein in NOB. The negative effects of bacterial communication, which were seriously ignored, have been highlighted, and Clp regulator downstream diffusible signal factor (DSF) based signal pathways worked as transcription activators and inhibitors of adaptation genes in AOB and NOB respectively. Bacterial communication can induce differential adaptation through influencing bacterial interactions. AOB inclined to cooperate with DSF synthesis bacteria as temperature declined, however, cooperation between NOB and DSF synthesis bacteria inclined to get weakening. According to the regulatory effects of signal pathways, bacterial survival strategies for self-protection were revealed. This study hints a potential way to govern niche differentiation in the microbiota by bacterial communication, contributing to forming an efficient artificial ecosystem.

Extending the Potency and Lifespan of Antibiotics: Inhibitors of Gram-Negative Bacterial Efflux Pumps.

Efflux is a natural process found in all prokaryotic and eukaryotic cells that removes a diverse range of substrates from inside to outside. Many antibiotics are substrates of bacterial efflux pumps, and modifications to the structure or overexpression of efflux pumps are an important resistance mechanism utilized by many multidrug-resistant bacteria. Therefore, chemical inhibition of bacterial efflux to revitalize existing antibiotics has been considered a promising approach for antimicrobial chemotherapy over two decades, and various strategies have been employed. In this review, we provide an overview of bacterial multidrug resistance (MDR) efflux pumps, of which the resistance nodulation division (RND) efflux pumps are considered the most clinically relevant in Gram-negative bacteria, and describe over 50 efflux inhibitors that target such systems. Although numerous efflux inhibitors have been identified to date, none have progressed into clinical use because of formulation, toxicity, and pharmacokinetic issues or a narrow spectrum of inhibition. For these reasons, the development of efflux inhibitors has been considered a difficult and complex area of research, and few active preclinical studies on efflux inhibitors are in progress. However, recently developed tools, including but not limited to computational tools including molecular docking models, offer hope that further research on efflux inhibitors can be a platform for research and development of new bacterial efflux inhibitors.

Effects of antipsychotics on the gastrointestinal microbiota: A systematic review.

Antipsychotics (APs) have been increasingly prescribed for psychiatric disorders from schizophrenia to disruptive behavioral conditions. These drugs have been associated with considerable side effects, such as weight gain, and increasing evidence has also indicated that its use impacts gut microbiota (GM), although this connection is still little understood. To assess APs effects on the GM of patients starting or ongoing treatment, a systematic review was carried out in PubMed and Scopus databases. Twelve articles were considered eligible for the review, which investigated the effects of risperidone (5 studies), quetiapine (3), amilsupride (1), olanzapine (1), and unspecified atypical drugs (2). Eleven reported changes in GM in response to APs, and associations between the abundance of bacterial groups and different metabolic parameters were described by most of them. However, the studies were noticeably heterogeneous considering design, methods, and results. In this way, the effects of APs on GM composition and diversity were inconclusive. Despite the uncertain interactions, a more comprehensive understanding on how microbiota is affected by APs may help to optimize treatment, potentially minimizing side effects and improving adherence to treatment.

Nitrogen-fixing cyanobacteria enhance microbial carbon utilization by modulating the microbial community composition in paddy soils of the Mollisols region.

Nitrogen-fixing cyanobacteria (NFC) are photosynthetic prokaryotic microorganisms capable of nitrogen fixation. They can be used as biofertilizers in paddy fields, thereby improving the rice tillering capacity and yield. To reveal the microbiological mechanisms by which nitrogen-fixing cyanobacteria alter soil carbon storage, we conducted a field experiment using NFC as a partial substitute for nitrogen fertilizer in paddy fields in the Sanjiang Plain of Northeast China's Mollisols region. Using metagenomic sequencing technology and Biolog Ecoplate™ carbon matrix metabolism measurements, we explored the changes in the soil microbial community structure and carbon utilization in paddy fields. The results indicated that the replacement of nitrogen fertilizer with NFC predisposed the soil microbial community to host a great number of copiotrophic bacterial taxa, and Proteobacteria and Actinobacteria were closely associated with the metabolism of soil carbon sources. Moreover, through co-occurrence network analysis, we found that copiotrophic bacteria clustered in modules that were positively correlated with the metabolic level of carbon sources. The addition of NFC promoted the growth of copiotrophic bacteria, which increased the carbon utilization level of soil microorganisms, improved the diversity of the microbial communities, and had a potential impact on the soil carbon stock. The findings of this study are helpful for assessing the impact of NFC on the ecological function of soil microbial communities in paddy fields in the black soil area of Northeast China, which is highly important for promoting sustainable agricultural development and providing scientific reference for promoting the use of algal-derived nitrogen fertilizers.

Responses of physiological, microbiome and lipid metabolism to lignocellulose wastes in gut of yellow mealworm (Tenebrio molitor).

There is limited research on physiological and degradation mechanisms of yellow mealworm, a novel organic waste converter, in processing lignocellulosic wastes. This study has selected two types of lignocellulosic wastes, distillers' grains (DG) and maize straw (MS), to feed yellow mealworms. This study investigated the effects of lignocellulosic wastes on the growth, antioxidant system, microbiome, and lipidome of yellow mealworms. The relative growth of lignocellulosic waste group was not significantly different from wheat bran. The antioxidant level was elevated in DG. MS was significantly enriched in cellulose-degrading bacteria in the gut and was accompanied by disturbances in lipid metabolism. The correlation coefficients were used to construct a network connecting diet, microbiota, and lipids. The correlation analysis indicated that two sphingolipids, hexylglyceramide and dihydroglyceramide, were strongly and positively linked with the dominating species. This study provides comprehensive information on physiological and mechanism of mealworms in process of treating lignocellulosic waste.

Synergistic antibacterial and antifouling wound dressings: Integration of photothermal-activated no release and zwitterionic surface modification.

Addressing the pervasive issue of bacteria and biofilm infections is crucial in the development of advanced antifouling wound dressings. In this study, a novel wound healing treatment using sulfobetaine (SBMA) decorated electrospun fibrous membrane based on polycaprolactone (PCL)/nitric oxide (NO) donors was developed. The fabrication involved a dual strategy, first integrating NO donors into mesoporous polydopamine (MPDA) and complexed with PCL/PEI to electrospin nanofibers. The fibrous membrane exhibited a potent antibacterial response upon irradiation at 808 nm, owing to a combination of NO and photothermal effect that effectively targets bacteria and disrupts biofilms. Surface functionalization of the membrane with PEI allowed for the attachment of SBMA via Michael addition, fabricating a zwitterionic surface, which significantly hinders protein adsorption and reduces biofilm formation on the wound dressing. In vitro and in vivo assessments confirmed the rapid bactericidal capabilities and its efficacy in biofilm eradication. Combining photothermal activity, targeted NO release and antifouling surface, this multifaceted wound dressing addresses key challenges in bacterial infection management and biofilm eradication, promoting efficient wound healing.

Characterization of multilayer bacterial cellulose-chitosan films loaded with grape bagasse antioxidant extract: Insights into spectral and water properties, microstructure, and antioxidant activity.

This work explores the development and characterization of composite multilayer films comprising bacterial cellulose (BC) and chitosan enriched with antioxidant compounds from grape bagasse extract (GE) and glycerol. SEM images revealed a compact structure with successful interactions between BC and chitosan, confirmed by FT-IR analysis. Equilibrium moisture content, water vapor permeability (WVP), swollen capacity, and solubility were systematically investigated, unveiling the influence of glycerol and GE concentrations. Moisture content increased with elevated glycerol and GE levels, attributed to their hydrophilic nature. WVP rose with higher concentrations of hydrophilic compounds, affecting the films' permeability. Swollen capacity decreased, and solubility increased with the addition of GE and glycerol, indicating a more compact film structure. The incorporation of GE conferred antioxidant properties to the films, as evidenced by DPPH and ABTS+ assays, and Total Phenolic Content (TPC) determination. TPC values varied from 0 to 1.75 mg GAE/g dried film, depending on GE. Fourier Transform Infrared Spectroscopy (FT-IR) highlighted polymeric associations, and UV-Vis spectra demonstrated enhanced UV-blocking properties. Overall, these multilayer films offer promising applications in food packaging, leveraging natural antioxidant sources for an enhanced functionality.

Cinnamaldehyde: an effective component of Cinnamomum cassia inhibiting Helicobacter pylori.

ETHNOPHARMACOLOGICAL RELEVANCE: Cinnamomum cassia Presl (Cinnamomum cassia) is a common traditional Chinese medicine, which can promote the secretion and digestion of gastric juice, improve the function of gastrointestinal tract. Cinnamaldehyde (CA) is a synthetic food flavoring in the Chinese Pharmacopoeia. AIM OF THE STUDY: This study aimed to search for the active ingredient (CA) of inhibiting H. pylori from Cinnamomum cassia, and elucidate mechanism of action, so as to provide the experimental basis for the treatment of H. pylori infection with Cinnamomum cassia. MATERIALS AND METHODS: It's in vitro and in vivo pharmacological properties were evaluated based on minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and an acute gastric inflammation model in mice infected with H. pylori. Drug safety was evaluated using the CCK8 method and high-dose administration in mice. The advantageous characteristics of CA in inhibiting H. pylori were confirmed using acidic conditions and in combination with the antibiotics. The mechanism underlying the action of CA on H. pylori was explored using scanning electron microscopy (SEM), adhesion experiments, biofilm inhibition tests, ATP and ROS release experiments, and drug affinity responsive target stability (DARTS) screening of target proteins. The protein function and target genes were verified by molecular docking and Real-Time quantitative reverse transcription PCR (qRT-PCR). RESULTS: The results demonstrated that CA was found to be the main active ingredient against H. pylori in Cinnamomum cassia in-vitro tests, with a MIC of 8-16 µg/mL. Moreover, CA effectively inhibited both sensitive and resistant H. pylori strains. The dual therapy of PPI + CA exhibited remarkable in vivo efficacy in the acute gastritis mouse model, superior to the standard triple therapy. DARTS, molecular docking, and qRT-PCR results suggested that the target sites of action were closely associated with GyrA, GyrB, AtpA, and TopA, which made DNA replication and transcription impossible, then leading to inhibition of bacterial adhesion and colonization, suppression of biofilm formation, and inhibition ATP and enhancing ROS. CONCLUSIONS: This study demonstrated the suitability of CA as a promising lead drug against H. pylori, The main mechanisms can target GyrA ect, leading to reduce ATP and produce ROS, which induces the apoptosis of bacterial.

Efficacy of non-instrumental Endodontic treatment in primary teeth: a systematic review of clinical randomized trials.

BACKGROUND: Endodontic therapy in pediatric dentistry is a challenging procedure, especially for special needs, uncooperative, and very young patients. A new conservative approach which is the non-instrumental endodontic treatment (NIET) has been developed to simplify the management of primary teeth requiring pulpectomy. This review aimed to compare the efficiency of NIET and conventional endodontic treatment in primary teeth. METHODS: Electronic databases including MEDLINE (via PubMed), Cochrane Library (CENTRAL), and Scopus without restrictions on publication year or publication language were searched. Only randomized clinical trials reporting clinical and radiographical outcomes of NIET and conventional pulpectomy on primary teeth were considered eligible. Two reviewers extracted the data according to the PRISMA statement and assessed the bias risk using the revised Cochrane risk-of-bias tool and a meta-analysis was performed. RESULTS: From 3322 screened articles, seven articles meeting the inclusion criteria were included. The selected studies included 283 primary molars, of 213 children aged between 3 and 9 years, treated by NIET and conventional pulpectomy, and had follow-up periods ranging from 1 month to tooth exfoliation. Two studies reported good success rates for both the NIET technique and endodontic therapy with no statistically significant difference while three studies showed radiographical significant differences with a low success rate for the NIET technique. Only one study reported better outcomes in the pulpectomy group with statistically significant differences. The quantitative grouping of the included studies showed no significant differences between NIET and conventional endodontic therapy regarding clinical and radiographical success (p value > 0.05). CONCLUSION: No difference between the NIET technique and the conventional endodontic therapy in primary molars requiring pulpectomy could be confirmed. Results of the present review need to be interpreted with caution since the quality of evidence according to the GRADE was considered as moderate to very low. Therefore, additional clinical trials on the NIET technique are recommended.

House of CarDs: Functional insights into the transcriptional regulator CdnL.

Regulation of bacterial transcription is a complex and multi-faceted phenomenon that is critical for growth and adaptation. Proteins in the CarD_CdnL_TRCF family are widespread, often essential, regulators of transcription of genes required for growth and metabolic homeostasis. Research in the last decade has described the mechanistic and structural bases of CarD-CdnL-mediated regulation of transcription initiation. More recently, studies in a range of bacteria have begun to elucidate the physiological roles of CarD-CdnL proteins as well as mechanisms by which these proteins, themselves, are regulated. A theme has emerged wherein regulation of CarD-CdnL proteins is central to bacterial adaptation to stress and/or changing environmental conditions.

Meeting report 'Microbiology 2023: from single cell to microbiome and host', an international interacademy conference in Würzburg.

On September 20-22 September 2023, the international conference 'Microbiology 2023: from single cell to microbiome and host' convened microbiologists from across the globe for a very successful symposium, showcasing cutting-edge research in the field. Invited lecturers delivered exceptional presentations covering a wide range of topics, with a major emphasis on phages and microbiomes, on the relevant bacteria within these ecosystems, and their multifaceted roles in diverse environments. Discussions also spanned the intricate analysis of fundamental bacterial processes, such as cell division, stress resistance, and interactions with phages. Organized by four renowned Academies, the German Leopoldina, the French Académie des sciences, the Royal Society UK, and the Royal Swedish Academy of Sciences, the symposium provided a dynamic platform for experts to share insights and discoveries, leaving participants inspired and eager to integrate new knowledge into their respective projects. The success of Microbiology 2023 prompted the decision to host the next quadrennial academic meeting in Sweden. This choice underscores the commitment to fostering international collaboration and advancing the frontiers of microbiological knowledge. The transition to Sweden promises to be an exciting step in the ongoing global dialogue and specific collaborations on microbiology, a field where researchers will continue to push the boundaries of knowledge, understanding, and innovation not only in health and disease but also in ecology.

Inhibitory effects of glutathione peroxidase on microbial spoilage of crayfish (Procambarus clarkii) during refrigerated storage.

The variety of enzyme-based biological preservatives is limited. This study evaluated the effects of glutathione peroxidase (GSH-Px) on the quality of crayfish during refrigerated storage by measuring the pH, total volatile basic nitrogen, trimethylamine, and microbial contamination in crayfish muscle simulation system. The results revealed that 0.3% GSH-Px (CK3) not only suppressed the degradation of nitrogenous substances but also decreased the contamination levels of total viable, Enterobacteriaceae, and Pseudomonas counts (P < 0.05). Furthermore, the populations of Lactococcus, Aeromonas, and Massilia differed in the CK3 group compared to the other groups (P < 0.05) at the end of the storage (day 15). Moreover, the principal coordinate analysis showed that the colony composition of CK3 stored for 15 days was similar to that of the control group stored for 10 days. Therefore, GSH-Px exhibits antibacterial activity against Gram-negative bacteria and has good application potential in freshwater aquatic product preservation.

New strontium-based coatings show activity against pathogenic bacteria in spine infection.

Infections of implants and prostheses represent relevant complications associated with the implantation of biomedical devices in spine surgery. Indeed, due to the length of the surgical procedures and the need to implant invasive devices, infections have high incidence, interfere with osseointegration, and are becoming increasingly difficult to threat with common therapies due to the acquisition of antibiotic resistance genes by pathogenic bacteria. The application of metal-substituted tricalcium phosphate coatings onto the biomedical devices is a promising strategy to simultaneously prevent bacterial infections and promote osseointegration/osseoinduction. Strontium-substituted tricalcium phosphate (Sr-TCP) is known to be an encouraging formulation with osseoinductive properties, but its antimicrobial potential is still unexplored. To this end, novel Sr-TCP coatings were manufactured by Ionized Jet Deposition technology and characterized for their physiochemical and morphological properties, cytotoxicity, and bioactivity against Escherichia coli ATCC 8739 and Staphylococcus aureus ATCC 6538P human pathogenic strains. The coatings are nanostructured, as they are composed by aggregates with diameters from 90 nm up to 1 µm, and their morphology depends significantly on the deposition time. The Sr-TCP coatings did not exhibit any cytotoxic effects on human cell lines and provided an inhibitory effect on the planktonic growth of E. coli and S. aureus strains after 8 h of incubation. Furthermore, bacterial adhesion (after 4 h of exposure) and biofilm formation (after 24 h of cell growth) were significantly reduced when the strains were cultured on Sr-TCP compared to tricalcium phosphate only coatings. On Sr-TCP coatings, E. coli and S. aureus cells lost their organization in a biofilm-like structure and showed morphological alterations due to the toxic effect of the metal. These results demonstrate the stability and anti-adhesion/antibiofilm properties of IJD-manufactured Sr-TCP coatings, which represent potential candidates for future applications to prevent prostheses infections and to promote osteointegration/osteoinduction.

Unlocking the genome of the non-sourdough Kazachstania humilis MAW1: insights into inhibitory factors and phenotypic properties.

BACKGROUND: Ascomycetous budding yeasts are ubiquitous environmental microorganisms important in food production and medicine. Due to recent intensive genomic research, the taxonomy of yeast is becoming more organized based on the identification of monophyletic taxa. This includes genera important to humans, such as Kazachstania. Until now, Kazachstania humilis (previously Candida humilis) was regarded as a sourdough-specific yeast. In addition, any antibacterial activity has not been associated with this species. RESULTS: Previously, we isolated a yeast strain that impaired bio-hydrogen production in a dark fermentation bioreactor and inhibited the growth of Gram-positive and Gram-negative bacteria. Here, using next generation sequencing technologies, we sequenced the genome of this strain named K. humilis MAW1. This is the first genome of a K. humilis isolate not originating from a fermented food. We used novel phylogenetic approach employing the 18 S-ITS-D1-D2 region to show the placement of the K. humilis MAW1 among other members of the Kazachstania genus. This strain was examined by global phenotypic profiling, including carbon sources utilized and the influence of stress conditions on growth. Using the well-recognized bacterial model Escherichia coli AB1157, we show that K. humilis MAW1 cultivated in an acidic medium inhibits bacterial growth by the disturbance of cell division, manifested by filament formation. To gain a greater understanding of the inhibitory effect of K. humilis MAW1, we selected 23 yeast proteins with recognized toxic activity against bacteria and used them for Blast searches of the K. humilis MAW1 genome assembly. The resulting panel of genes present in the K. humilis MAW1 genome included those encoding the 1,3-ß-glucan glycosidase and the 1,3-ß-glucan synthesis inhibitor that might disturb the bacterial cell envelope structures. CONCLUSIONS: We characterized a non-sourdough-derived strain of K. humilis, including its genome sequence and physiological aspects. The MAW1, together with other K. humilis strains, shows the new organization of the mating-type locus. The revealed here pH-dependent ability to inhibit bacterial growth has not been previously recognized in this species. Our study contributes to the building of genome sequence-based classification systems; better understanding of K.humilis as a cell factory in fermentation processes and exploring bacteria-yeast interactions in microbial communities.

Corneal Deposits: A Presentation of Arthrobacter Keratitis.

Introduction: Infectious keratitis, an inflammatory condition of the cornea, poses a significant public health concern globally. Bacterial keratitis, the most common type, primarily involves Staphylococcus aureus and Pseudomonas aeruginosa. Timely diagnosis and treatment are crucial to prevent vision loss. Case Presentation: This case report presents a 78-year-old male patient with a burning sensation persisting for 1 week. The patient was diagnosed with keratitis caused by Arthrobacter, a Gram-positive coccobacillus commonly found in the environment. While the literature reports a few cases of Arthrobacter species keratitis, limited data exist regarding its clinical course and outcomes. Treatment with ciprofloxacin eye drops resulted in complete resolution of symptoms and a clear cornea upon final follow-up. Conclusion: Arthrobacter, a rare causative agent of keratitis, requires early suspicion for accurate diagnosis and treatment. Despite the limited literature on Arthrobacter keratitis, this case highlights the importance of considering uncommon pathogens in corneal infections. Further research is necessary to understand the prevalence and clinical course of Arthrobacter keratitis.