FEMS microbes最新文献

Anaerobic gut fungi (AGF, Neocallimastigomycota) inhabit the alimentary tract of herbivores. Although strict anaerobes, studies have suggested their capacity to retain viability after various durations of air exposure. It is currently unclear whether AGF can actively grow, and not merely survive, in redox potentials (E_h) higher than those encountered in the herbivorous gut. We evaluated the growth of two AGF strains (Orpinomyces joyonii and Testudinimyces gracilis) at various E_h levels, achieved by manipulating the concentrations of reductant (cysteine hydrochloride) in culture media. Both strains exhibited robust and sustainable growth at negative E_h (-50 mV or below). However, growth in the absence of cysteine hydrochloride (E_h value around +50 mV) was possible only for O. joyonii and only for one subcultivation. The capacity to grow at +50 mV was further confirmed in four additional taxa (Pecoramyces ruminatium, Anaeromyces mucronatus, Aklioshbmyces papillarum, and Piromyces communis), while two (Aestipascuomyces dupliciliberans and Capellomyces foraminis) failed to grow under these conditions. Our results establish the ability of AGF to grow at redox potential values higher than those encountered in their natural habitats. Such capability could contribute to efficient AGF dispersal and horizontal transmission between hosts, and could have important implications for industrial applications of AGF.

Important questions remain about the sources of transmission of pneumococcus to older adults in the community. This is critical for understanding the potential effects of using pneumococcal conjugate vaccines (PCVs) in children and older adults. For non-institutionalized individuals, we hypothesized that the most likely source of adult-to-adult transmission is within the household. We designed a longitudinal study to sample adults ≥60 years of age living in the same household (New Haven, CT, USA), without younger residents in the household. Saliva samples and social and health questionnaires were obtained every 2 weeks for a period of 10 weeks. DNA extracted from culture-enriched saliva was tested using qPCR for pneumococcus genes piaB, lytA, and serotype. Across two study seasons (November 2020-August 2021, November 2021-September 2022), 121 individuals from 61 households completed all six visits; 62 individuals were enrolled in both seasons. Overall, 52/1088 (4.8%) samples tested positive for pneumococcus, with 27/121 (22.3%) individuals colonized at least once. Several individuals were colonized at multiple time points; two individuals were colonized at 5/6 time points and two at all six. In 5 instances, both household members were carriers in the same season, though not necessarily at the same time. Pneumococcal carriage was substantially higher among individuals who had contact with children (10.0% vs. 1.6%). Contact with young children was the most important factor that influenced pneumococcal acquisition rates. While there were several instances where both adult household members were colonized at the same time or at sequential visits, these individuals typically had contact with children. As such, PCV immunization can directly protect older adults who have contact with children.

Enterococcus faecalis is ranked among the top five bacterial pathogens responsible for catheter-associated urinary tract infections, wound infections, secondary root canal infections, and infective endocarditis. Previously, we showed that inactivation of either the manganese- and iron-binding (EfaA) or zinc-binding (AdcA and AdcAII) lipoproteins significantly reduced E. faecalis virulence. Here, we explored whether immunization using a multi-valent approach induces protective immunity against systemic enterococcal infections. We found that multi-antigen antisera raised against EfaA, AdcA, and AdcAII displayed similar capacities to initiate neutrophil-mediated opsonization, like their single-antigen counterparts. Further, these antigen-specific antibodies worked synergistically with calprotectin, a divalent host metal chelator, to inhibit the growth of E. faecalis in laboratory media as well as in human sera. Using the Galleria mellonella invertebrate model and mouse peritonitis model, we showed that passive immunization with multi-antigen antisera conferred robust protection against E. faecalis infection, while the protective effects of single antigen antisera were negligible in G. mellonella, and negligible-to-moderate in the mouse model. Lastly, active immunization with the 3-antigen (trivalent) cocktail significantly protected mice against either lethal or non-lethal E. faecalis infections, with this protection appearing to be far-reaching based on immunization results obtained with contemporary strains of E. faecalis and closely related Enterococcus faecium.

Enterococcus faecalis is a commensal bacterium in the gastrointestinal (GI) tract of humans and other organisms. E. faecalis also causes infections in root canals, wounds, the urinary tract, and on heart valves. E. faecalis metabolizes arginine through the arginine deiminase pathway, which converts arginine to ornithine and releases ATP, ammonia, and CO₂. E. faecalis arginine metabolism also affects virulence of other pathogens during co-culture. E. faecalis may encounter elevated levels of arginine in the GI tract or the oral cavity, where arginine is used as a dental therapeutic. Little is known about how E. faecalis responds to growth in arginine in the absence of other bacteria. To address this, we used RNAseq and additional assays to measure growth, gene expression, and biofilm formation in E. faecalis OG1RF grown in arginine. We demonstrate that arginine decreases E. faecalis biofilm production and causes widespread differential expression of genes related to metabolism, quorum sensing, and polysaccharide synthesis. Growth in arginine also increases aggregation of E. faecalis and promotes decreased susceptibility to the antibiotics ampicillin and ceftriaxone. This work provides a platform for understanding how the presence of arginine in biological niches affects E. faecalis physiology and virulence of surrounding microbes.

Student engagement is one of the critical issues in science classes. This commentary explores the value of storytelling in microbiology education and student engagement. It is a result of an undergraduate exercise, where students were asked to draft short stories on pandemics before the COVID-19 pandemic (i.e. conducted in 2016-2019). The analysis of student writings (total of 244 short stories) aimed to understand the students' perception of pandemics, the diseases they chose to write about, and their level of knowledge of pandemics. Interestingly, 56.6% of students chose viruses to be the cause of their pandemics, 35.7% chose bacteria, 4.5% chose parasites, and a single student chose a fungus. Respiratory mode of transmission was the top pick in the stories (30%), followed by fecal-oral route, sexually transmitted, and skin-to-skin contact. Therefore, their choice of respiratory diseases as the focus of their short story may suggest their limited understanding of pandemics beyond such diseases. The varying levels of detail in the stories suggested that storytelling could be insightful in identifying knowledge gaps and engaging students. Two exciting questions remain: (1) For the students who wrote those short stories before the COVID-19 pandemic, how did they feel when it hit? (2) If the students are asked again to write a pandemic short story, what would it look like nowadays? A deeper understanding of epidemiology and the social impact of pandemics is crucial for developing effective pandemic preparedness and response plans, and undergraduate courses can play a vital role in this endeavor. Overall, this commentary highlights the value of storytelling in engaging students to assess their knowledge of specific subject matters.

Neocallimastigomycota are a phylum of anaerobic gut fungi (AGF) that inhabit the gastrointestinal tract of herbivores and play a pivotal role in plant matter degradation. Their identification and characterization with marker gene regions has long been hampered due to the high inter- and intraspecies length variability in the commonly used fungal marker gene region internal transcribed spacer (ITS). While recent research has improved methodology (i.e. switch to LSU D2 as marker region), molecular methods will always introduce bias through nucleic acid extraction or PCR amplification. Here, near-infrared spectroscopy (NIRS) and hyperspectral imaging (HSI) are introduced as two nucleic acid sequence-independent tools for the characterization and identification of AGF strains. We present a proof-of-concept for both, achieving an independent prediction accuracy of above 95% for models based on discriminant analysis trained with samples of three different genera. We further demonstrated the robustness of the NIRS model by testing it on cultures of different growth times. Overall, NIRS provides a simple, reliable, and nondestructive approach for AGF classification, independent of molecular approaches. The HSI method provides further advantages by requiring less biomass and adding spatial information, a valuable feature if this method is extended to mixed cultures or environmental samples in the future.

The gastrointestinal tract (GIT) is typically considered the natural niche of enterococci. However, these bacteria also inhabit extraintestinal tissues, where they can disrupt organ physiology and cause life-threatening infections. Here, we discuss how enterococci, primarily Enterococcus faecalis, interact with the intestine and other host anatomical locations such as the oral cavity, heart, liver, kidney, and vaginal tract. The metabolic flexibility of these bacteria allows them to quickly adapt to new environments, promoting their persistence in diverse tissues. In transitioning from commensals to pathogens, enterococci must overcome harsh conditions such as nutrient competition, exposure to antimicrobials, and immune pressure. Therefore, enterococci have evolved multiple mechanisms to adhere, colonize, persist, and endure these challenges in the host. This review provides a comprehensive overview of how enterococci interact with diverse host cells and tissues across multiple organ systems, highlighting the key molecular pathways that mediate enterococcal adaptation, persistence, and pathogenic behavior.

Yarrowia lipolytica is a well-characterized yeast with remarkable metabolic adaptability. It is capable of producing various products from different carbon sources and easily switching between planktonic and biofilm states. A biofilm represents a natural means of cell immobilization that could support continuous cultivation and production processes, such as perfusion cultivation. However, the metabolic activities of Y. lipolytica in biofilms have not yet been studied in detail. Therefore, this study aimed to compare the metabolic activities of Y. lipolytica in biofilm and planktonic states. Conventionally, a stirred tank bioreactor was used to cultivate Y. lipolytica in a planktonic state. On the other hand, a trickle bed bioreactor system was used for biofilm cultivation. The low pH at 3 was maintained to favor polyol production. The accumulation of citric acid was observed over time only in the biofilm state, which significantly differed from the planktonic state. Although the biofilm cultivation process has lower productivity, it has been observed that the production rate remains constant and the total product yield is comparable to the planktonic state when supplied with 42% oxygen-enriched air. This finding indicates that the biofilm state has the potential for continuous bioprocessing applications and is possibly a feasible option.

Marine sediments have been suggested as a reservoir for pathogenic bacteria, including Escherichia coli. The origins, and properties promoting survival of E. coli in marine sediments (including osmotolerance, biofilm formation capacity, and antibiotic resistance), have not been well-characterized. Phenotypes and genotypes of 37 E. coli isolates from coastal marine sediments were characterized. The isolates were diverse: 30 sequence types were identified that have been previously documented in humans, livestock, and other animals. Virulence genes were found in all isolates, with more virulence genes found in isolates sampled from sediment closer to the effluent discharge point of a wastewater treatment plant. Antibiotic resistance was demonstrated phenotypically for one isolate, which also carried tetracycline resistance genes on a plasmid. Biofilm formation capacity varied for the different isolates, with most biofilm formed by phylogroup B1 isolates. All isolates were halotolerant, growing at 3.5% NaCl. This suggests that the properties of some isolates may facilitate survival in marine environments and can explain in part how marine sediments can be a reservoir for pathogenic E. coli. As disturbance of sediment could resuspend bacteria, this should be considered as a potential contributor to compromised bathing water quality at nearby beaches.

The significance of heme to Enterococcus faecalis is reviewed while also identifying the prevalence of hemoproteins throughout the enterococci and highlighting gaps in knowledge in enterococcal mechanisms of heme homeostasis.