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At least 19 recordsLinked to original sources

bioRxiv2022

A bibliometric analysis of gender in microbiology collaborations

Women are underrepresented in senior academic positions within microbiology globally. Studies show that gender bias affects the progression of women in academia, but there is evidence that improving conscious awareness of bias can improve equity in this regard. Here we carry out a bibliometric analysis of review articles within the microbiology field to investigate the statistical associations with author gender. We analyse the publication data from 1857 review articles published between 2010 and 2022 in three leading microbiology review journals: Nature Reviews Microbiology, Trends in Microbiology, and Annual Review of Microbiology. We find a significant association between the gender of the lead author and the gender of co-authors in multi-author publications. Review articles with men lead authors have a significantly reduced proportion of women co-authors compared to reviews with women lead authors. Given the existing differences in the proportions of men and women in lead author positions, this association may have important consequences for the relative visibility of women in microbiology, along with potential negative impacts on scientific output relating to reduced collaboration diversity. We further probe associations between gender and citation metrics, acknowledgement of contributions, and publishing during the Covid-19 pandemic within microbiology reviews.

scientific communication and education↗

bioRxiv2024

Bacttle: a microbiology educational board game for lay public and schools

1.Inspired by the positive impact of serious games on science understanding and motivated by personal interests in scienti[fi]c outreach, we developed Bacttle, an easy-to-play microbiology board game with adaptive difficulty, targeting any player from 7 years old onward. Bacttle addresses both the lay public and teachers for use in classrooms as a way of introducing microbiology concepts. The layout of the game and its mechanism are the result of multiple rounds of trial, feedback and re-design. The [fi]nal version consists of a deck of cards, a 3D-printed board and tokens (with a paper-based alternative), with all digital content open source. Players in Bacttle take on the character of a bacterial species. The aim for each species is to proliferate under the environmental conditions of the board and the interactions with the board and with other players, which vary as the play evolves. Players start with a given number of lives that will increase or decrease based on the traits they play for different environmental scenarios. Such bacterial traits come in the form of cards that can be deployed strategically. In order to assess the impact of the game on microbiological knowledge, we scored differences in the understanding of general concepts before and after playing the game. We assessed a total of 169 visitors at two different university open day science fairs. Players were asked to [fi]ll a brief survey before and after the game with questions targeting conceptual advances. Results show that Bacttle increases general microbiology knowledge on players as young as 5 years old, and with the highest impact on those who have no a priori microbiology comprehension.

scientific communication and education↗

bioRxiv2020

ICP-MS analysis of metal and metalloid concentrations of common microbiological growth media reveals presence of heavy metals

Trace elements such as cobalt and manganese play important roles as cofactors of enzymes, and thus, they collectively impact on biochemistry and cellular metabolism. Hence, it is of importance to gain an understanding of the trace metal and metalloid concentrations of growth medium in order to fully account for the growth performance of the bacterium. But, this aspect of microbial cell cultivation is usually neglected. Advent of instrumented techniques for metals and metalloid analysis such as inductively coupled plasma mass spectrometry (ICP-MS) has significantly facilitated trace element analysis at the parts per billion (ppb) to parts per million (ppm) level in aqueous matrixes free of organic interference. In this work, ICP-MS was utilized as the principal tool for profiling the range of metals and metalloids in different microbiological growth medium ranging from minimal salts medium to complex chemically undefined medium. Growth media examined include: LB Lennox, LB Lennox + 2 g/L glucose, LB Lennox (buffered, 89 mM phosphate), LB Lennox (buffered, 89 mM phosphate) + 6 g/L glucose, formulated medium + 6 g/L glucose, Tryptic Soy Broth, M9 medium, and M9 + 1 g/L yeast extract medium. Results reveal detection of elevated concentrations of chromium, copper and cadmium in different versions of LB Lennox and Tryptic Soy Broth. Concentrations of the above heavy metals in the tens of ppm range meant that the growth media could only support the growth of environmental bacteria with some resistance to heavy metal toxicity. On the other hand, no heavy metals were detected in M9 minimal salts medium or a modified version with supplementation of 1 g/L yeast extract. This indicated that minimal salts media may have less of a problem with heavy metal contamination compared to chemically undefined microbiological growth media. Collectively, the results highlight the essentiality of conducting a comprehensive profiling experiment for detecting different metals and metalloids at trace levels in microbiological growth medium. Such data would in addition to offering a deeper understanding of some peculiar growth behaviour from some microorganisms, may also help identify contamination issue during manufacture that preclude use of the media in cultivating many laboratory domesticated microorganisms. Subject areasbiochemistry, biotechnology, cell biology, microbiology, biochemical engineering,

microbiology↗

bioRxiv2026

Validation of an AI-Powered Automated Colony Analysis Platform Across Eight ISO Microbiological Methods: A Multi-Pathogen, Multi-Matrix Performance Study

Manual colony counting remains the rate-limiting, operator-dependent step in culture-based food microbiology quality control (QC). Automated colony analysis using machine learning (ML) offers the potential to standardise, accelerate, and improve the traceability of this process. However, systematic multi-method validation data for AI-based platforms against recognised international standards remain scarce. We conducted a prospective, multi-study validation of the Reshape Smart Incubator which is an automated imaging and ML-based colony analysis system, across eight ISO microbiological reference methods. In total, 887 plates were analysed, spanning qualitative (presence/absence) detection of Listeria spp. (ISO 11290-1) and Salmonella spp. (ISO 6579), and quantitative enumeration of total viable count (ISO 4833), Bacillus cereus (ISO 7932), Enterobacteriaceae (ISO 21528), coagulase-positive Staphylococci (ISO 6888), yeasts and moulds (ISO 21527), and lactic acid bacteria (ISO 15214). Automated results were benchmarked against the consensus of three or more trained technicians. The platform achieved 100% agreement with manual assessment for all both qualitative detection methods (ISO 11290-1, ISO 6579) with zero false positives and zero false negatives. For quantitative enumeration, agreement ranged from 92.97% (ISO 15214, n=122, using ISO-aligned {+/-}10%/>30 CFU thresholds) to 98.46% (ISO 21528, n=130). Where discrepancies occurred, they largely coincided with plates showing high inter-technician variability. Precision testing demonstrated a coefficient of variation of 5.88% and a mean standard deviation of 0.44 CFU for low-count plates. This study presents a comprehensive multi-ISO validation of an AI-based colony analysis system to date. The AI models demonstrated performance comparable to or exceeding that of trained human technicians across a broad range of microbiological targets, agar types, and colony morphologies, thereby supporting their use as a validated and traceable alternative to manual plate reading in accredited food microbiology quality control laboratories.

microbiology↗

bioRxiv2018

Redesign of an Undergraduate General Microbiology Lab to Include Authentic Discovery-Driven Research on Cucumber Fermentations

Many undergraduate introductory microbiology laboratory courses teach basic principles of bacteriology using classical protocol-based experiments, with limited critical thinking and inquiry-based learning practices. We initiated a comprehensive redesign in our General Microbiology Laboratory course to promote scientific critical and creative thinking, while strengthening core microbiology concepts and skills. As part of the redesign, a series of authentic discovery-driven labs, based on cucumber fermentations, were developed as an independent research module within the course curriculum. Integrating discovery-driven labs allowed students to be engaged problem solvers, applying the scientific process to develop hypotheses, design experiments, utilize quantitative reasoning, and effectively communicate results. The inquiry-guided research project was developed to evaluate the minimum concentration of salt (NaCl) required in fermentation brine to safely, and effectively, ferment cucumbers. Over 5 weeks, students assess different aspects of the fermentation process, including quantifying bacterial populations with differential and selective media, measuring pH and glucose concentration of brine solutions, and characterizing the microbial metabolic potential. Additionally, students isolate an unknown bacterium from their fermentations, identifying and characterizing the isolate using 16S rRNA gene sequencing and metabolic tests. Throughout the research project, students collect, graph, and analyze their observations, culminating in students creating and presenting a scientific research poster. With this lab redesign, students generate new knowledge contributing to our understanding of microbial ecology within food fermentations, learn core microbiology skills and techniques, and develop critical and creative thinking skills. The impact of their research is valuable to science educators, researchers, and industry partners.

scientific communication and education↗

bioRxiv2026

Sustained Improvements in Student Outcomes Following Integration of Clinical Case Narratives in Veterinary Microbiology Curriculum

Microbiology education in veterinary curricula requires students to integrate complex foundational knowledge with clinical application, yet traditional lecture-based approaches often emphasize memorization over higher-order reasoning. In this study, we evaluated the impact of integrating clinically oriented, case-based instruction into a veterinary microbiology course within a Doctor of Veterinary Medicine curriculum. Using a quasi-experimental, multi-year design, student outcomes were compared before (2019, 2021) and after (2022-2025) implementation of case-based teaching while maintaining consistent course content, structure, and assessments. Introduction of clinical case examples was associated with significant and sustained improvements in student evaluations across multiple domains, including perceived relevance, critical thinking, and overall course value. Instructor-related evaluation metrics also improved. Student performance, measured by final course grades, increased following the intervention without evidence of grade inflation. These findings demonstrate that integrating clinically relevant case narratives into microbiology instruction enhances student engagement and student performance. This work highlights a practical and scalable strategy for improving microbiology education, particularly within veterinary and other health-professions curricula.

scientific communication and education↗

bioRxiv2015

Revolutionising Public Health Reference Microbiology using Whole Genome Sequencing: Salmonella as an exemplar

Advances in whole genome sequencing (WGS) platforms and DNA library preparation have led to the development of methods for high throughput sequencing of bacterial genomes at a relatively low cost (Loman et al. 2012; Medini et al. 2008). WGS offers unprecedented resolution for determining degrees of relatedness between strains of bacterial pathogens and has proven a powerful tool for microbial population studies and epidemiological investigations (Harris et al. 2010; Lienau et al. 2011; Holt et al. 2009; Ashton, Peters, et al. 2015). The potential utility of WGS to public health microbiology has been highlighted previously (Koser et al. 2012; Kwong et al. 2013; Reuter et al. 2013; Joensen et al. 2014; Nair et al. 2014; Bakker et al. 2014; DAuria et al. 2014). Here we report, for the first time, the routine use of WGS as the primary test for identification, surveillance and outbreak investigation by a national reference laboratory. We present data on how this has revolutionised public health microbiology for one of the most common bacterial pathogens in the United Kingdom, the Salmonellae.\n\nDATA SUMMARY1. PHE Salmonella sequencing data is deposited in the Sequence Read Archive in BioProject PRJNA248792.\n\nIMPACT STATEMENTThe first human genome cost around $3 billion, and took around 10 years to complete. Advances in DNA sequencing technology (also referred to as whole genome sequencing (WGS)) allow the same feat to be accomplished today for less than $10000 and less than 2 weeks. This remarkable improvement in technology has also led to a step change in microbiology, increasing our understanding of the evolution of major human pathogens such as Yersinia pestis, Salmonella Typhi and Mycobacterium tuberculosis. While these kinds of academic studies provide unparalleled context for public health action, until now, this approach has not been routinely employed at the frontline. At Public Health England, WGS has been implemented for routine public health identification, characterisation and typing of an important human pathogen, Salmonella, replacing methods that have changed little over the last 100 years. Analysis of WGS data has identified outbreaks that were previously undetectable and been used to infer rare antimicrobial resistance patterns. This paper will serve as a notification to the community of the methods PHE are using, and will be of great use to other public health labs considering switching to WGS.

Microbiology↗

bioRxiv2020

Bivariate confidence probability plots as a method to test the accuracy and variability of microbiological measures

IntroductionIn an interlaboratory calibration analysis to validate a methodology that will be proposed as a European standard for domestic laundry disinfection, tests were carried out to detect if there are different behaviors in the measurements regarding accuracies and variabilities. Interlaboratory tests using different doses of disinfectant and microorganisms were carried out. ISO 5725-2 and ISO 13528 form the basis of validations of quantitative methods, providing validation specifications for interlaboratory studies. However, a need for a simple graphical method to detect interlaboratory differences in accuracy and variability was observed. ObjectivesThe general goal of this work is to present a new exploratory methodology, graphical and easy to interpret, that can determine the accuracy and variability (precision) of a variable, and compare it to the methodology applied in ISO 5725-2 and ISO 13528. MethodsWe used confidence probability plots of the multivariate Students t-distribution to observe the accuracy and variability of microbiological measures carried out by different laboratories during a ring trial exercise. A function in R was built for this purpose: Miriam.analysis.ellipse(Y, factor_a, eel.plot = " t-Student"). The different observations of accuracy and variability are represented in the ellipses. If any of the points are outside the ellipse with 95% confidence, we can assume a deviation in accuracy and / or variability. ResultsTwo examples are provided with real microbiological data (logarithmic unit reductions (LR) for Pseudomonas aeruginosa, Escherichia coli, Staphilococcus aureus, Enterococcus hirae, Candida albicans and microbial counts in water (WW)). The proposed new method allowed us to detect possible deviations in the WWMEA variable and we believe it has future application for the rapid control of microbiological measures.

microbiology↗

bioRxiv2021

Clinical Phage Microbiology:A suggested framework and recommendations for the in-vitro matching steps ‎of phage therapy

Personalized-phage-therapy is a promising solution for the emerging crisis of bacterial infections that fail to be eradicated by conventional antibiotics. One of the most crucial elements of personalized-phage-therapy is the proper matching of phages and antibiotics to the target bacteria in a given clinical setting. However, to date, there is no consensus guideline for laboratory procedures that enable in vitro evaluation of phages intended for treatment. In this work, we suggest a framework and strategies identify appropriate phages and combine them with antibiotics in clinical microbiology laboratories. This framework, which we term here "Clinical Phage Microbiology" is based on our experience and other previously reported cases of both, successful and failed phage treatments. Additionally, we discuss troubleshooting methodologies for possible pitfalls and special cases that may need to be assessed before treatment including interactions with the host immune system, biofilms, and polymicrobial infections. We believe that the "Clinical Phage Microbiology" pipeline presented here should serve as the basis for standardization of laboratory protocols to match phages for personalized therapy.

microbiology↗

bioRxiv2023

Quantitative Microbiology with Microscopy: Effects of Projection and Diffraction

Time-resolved live-cell imaging using widefield microscopy is instrumental in quantitative microbiology research. It allows us to track and measure the size, shape, and content of individual microbial cells over time. However, the small size of microbial cells poses a significant challenge in interpreting image data, as it approaches the dimensions of the microscopes depth of field and experiences diffraction effects. As a result, 2D widefield images of microbial cells contain projected 3D information, blurred by the 3D point spread function. In this study, we employ computer simulations and targeted experiments to investigate the impact of diffraction and projection on our ability to quantify the size and content of microbial cells from 2D microscopic images. This study points to some new and often unconsidered artefacts resulting from the interplay of projection and diffraction effects, within the context of quantitative microbiology. These artefacts introduce substantial errors and biases in size and fluorescence quantification, and even single-molecule counting, making the elimination of these errors a complex task. Awareness of these artefacts is crucial for designing strategies to accurately interpret micrographs of microbes. To address this, we present new experimental designs and machine learning based analysis methods that account for these effects, resulting in accurate quantification of microbiological processes.

microbiology↗

bioRxiv2024

Simulating Offshore Oilfield Conditions: Insights into Microbiologically Influenced Corrosion from a Dual Anaerobic Biofilm Reactor

Oilfield systems are a multifaceted ecological niche which consistently experience microbiologically influenced corrosion. However, simulating environmental conditions of an offshore system within the laboratory is notoriously difficult. A novel dual anaerobic biofilm reactor protocol allowed a complex mixed-species marine biofilm to be studied. Interestingly, electroactive corrosive bacteria and fermentative electroactive bacteria growth was supported within the biofilm microenvironment. Critically, the biotic condition exhibited pits with a greater average area which is characteristic of microbiologically influenced corrosion. This research seeks to bridge the gap between experimental and real-world scenarios, ultimately enhancing the reliability of biofilm management strategies in the industry. ImportanceIt is becoming more widely understood that any investigation of microbiologically influenced corrosion requires a multidisciplinary focus on multiple lines of evidence. While there are numerous standards available to guide specific types of testing, there are none that focus on integrating biofilm testing. By developing a novel dual anaerobic reactor model to study biofilms, insights into the different abiotic and biotic corrosion mechanisms under relevant environmental conditions can be gained. Using multiple lines of evidence to gain a holistic understanding, more sustainable prevention and mitigation strategies can be designed. To our knowledge, this is the first time all these metrics have been combined in one unified approach. The overall aim for this paper is to explore recent advances in biofilm testing and corrosion research, to provide recommendations for future standards being drafted. However, it is important to note that this article itself is not intending to serve as a standard.

microbiology↗

bioRxiv2018

Fresh Snowfall Microbiology and Chemistry are Driven by Geography in Storm-Tracked Events

Snowfall is a global phenomenon highly integrated with hydrology and ecology. Forays into studying bioaerosols and their dependence on aeolian movement are largely constrained to either precipitation-independent analyses or in-silico models. Though snowpack and glacial microbiological studies have been conducted, little is known about the biological component of meteoric snow. Through culture-independent phylogenetic and geochemical analyses, we show that the geographical location at which snow precipitates determines snowfalls geochemical and microbiological composition. Storm-tracking, furthermore, can be used as a valuable environmental indicator to trace down what factors are influencing bioaerosols. We estimate annual deposits of up to ~10 kg of bacterial / archaeal biomass per hectare along our study area of the eastern Front Range in Colorado. The dominant kinds of microbiota captured in an analysis of seven snow events at two different locations, one urban, one rural, across the winter of 2016/2017 included phyla Proteobacteria, Bacteroidetes, Firmicutes and Acidobacteria, though a multitude of different kinds of organisms were found in both. Taxonomically, Bacteroidetes were more abundant in Golden (urban plain) snow while Proteobacteria were more common in Sunshine (rural mountain) samples. Chemically, Golden snowfall was positively correlated with some metals and anions. The work also hints at better informing the everything is everywhere hypotheses of the microbial world and that atmospheric transport of microbiota is not only common, but is capable of disseminating vast amounts of microbiota of different physiologies and genetics that then affect ecosystems globally. Snowfall, we conclude, is a significant repository of microbiological material with strong implications for both ecosystem genetic flux and general bio-aerosol theory.\n\nImportanceSnowfall is commonplace to the temperate and polar regions of the world. As an interface between the atmosphere, hydrosphere and earth, snow is responsible for high annual deposits of moisture globally, and, can serve as a water bank in the form of both permanent snow fields and glaciers. Essential to general ecosystem function, snow can also be considered a transporter of aerosolized material. Given the magnitude of microbiota deposited by snowfall, which we report, it is likely that biological material within snowfall, with its geochemical underpinning-- and the associated genetic banks--have significant downstream ecological effects.\n\nUnderstanding what is contained in snowfall becomes especially urgent in a warming climate where high-impact meteorological and ecological changes are imminent and likely. With climate-induced changes to snowfall patterns, surface ecosystems are likely to be impacted by ensuing changes in microbiota deposition. Thus, the ecosystem function of soils, rock and surface waters are also likely to be impacted; these changes, in turn, greatly influence agriculture, weathering and infrastructure.

microbiology↗

bioRxiv2019

Replicating Arabidopsis Model Leaf Surfaces for Phyllosphere Microbiology

Artificial surfaces are commonly used in place of leaves in phyllosphere microbiology to study microbial behaviour on plant leaf surfaces. Studies looking into individual environmental factors influencing microorganisms are routinely carried out using artificial surfaces. Commonly used artificial surfaces include nutrient agar, isolated leaf cuticles, and reconstituted leaf waxes. However, interest is growing in using microstructured surfaces mimicking the complex topography of leaf surfaces for phyllosphere microbiology. As such replica leaf surfaces, produced by microfabrication, are appearing in literature. Replica leaf surfaces have been produced in agar, epoxy, polystyrene, and polydimethylsiloxane (PDMS). However, these protocols are not suitable for replicating fragile leaves such as of the model plant Arabidopsis thaliana. This is of importance as A. thaliana is a model system for molecular plant genetics, molecular plant biology, and microbial ecology. Here we present a versatile replication protocol for replicating fragile leaf surfaces into PDMS. We display the capacity of our replication process using optical microscopy, atomic force microscopy (AFM), and contact angle measurements to compare living and PDMS replica A. thaliana leaf surfaces. To highlight the use of our replica leaf surfaces for phyllosphere microbiology, we visualised bacteria on the replica leaf surfaces in comparison to living leaf surfaces.

microbiology↗

bioRxiv2026

Microbiological Survey of the San Pedro Basin Subseafloor

Marine subseafloor sediments host extensive microbial communities that drive global biogeochemical processes. Despite its proximity to one of the most densely populated and economically important coastal regions in the world, the sub benthic ecology of the San Pedro Channel, the waterway separating Los Angeles County from Santa Catalina Island, remains largely uncharacterized. To establish the foundational knowledge required for future impact assessment studies, we initiated a sediment coring survey that generated a water and sediment depth standardized transect across the sloping flanks of the San Pedro Basin. Here, we describe the early development of an integrated subseafloor microbiological catalogue for this region of intense maritime activity incorporating molecular ecology, microbial isolation and cultivation, and physiological assays. This initial effort is designed not as a direct comparison between basin flanks, but as a baseline assessment that captures ecological and microbiological variation across paired sides matched in water column depth and sediment depth beneath seafloor. Accordingly, we provide a cross channel coordinated dataset of subseafloor microbial communities and cultivated representatives from San Pedro Basin sediment, offering a critical starting point for understanding natural variability and for detecting potential signatures of environmental or anthropogenic disturbance. Ultimately, this baseline will support long{square}term monitoring efforts and supply a curated collection of isolates for future experimental microbiology and comparative genomics research.

ecology↗

bioRxiv2026

Semantic networks as a tool for analyzing conceptual organization in active teaching methodologies in Microbiology

Active teaching methodologies have been widely used to promote meaningful learning and student autonomy. In this context, quantitative approaches can help assess how students organize and integrate knowledge throughout the learning process. Among these approaches, semantic co-occurrence networks stand out, as they are capable of identifying relationships between words and revealing the conceptual structure of textual productions. The objective of this study was to investigate whether semantic network analyses can characterize differences in students conceptual organization in Microbiology during their participation in the active teaching methodology "Adopt a Bacterium." To this end, a case study was conducted in the Bacteriology course at the Institute of Biomedical Sciences of the University of Sao Paulo, analyzing the textual productions of two groups of students in the years 2024 and 2025 during their study of the bacterial genus Bacillus. The texts were evaluated using semantic co-occurrence networks, taking into account metrics of structure and conceptual integration. The results showed that both groups covered the microbiological content outlined in the course, though with different thematic focuses and approaches to integrating the concepts. Although both years featured modular structures (a statistical mode of 9 subgraphs), in 2025 the network exhibited greater discursive robustness (2 to 4 times more words with high Betweenness centrality) than in 2024. It is concluded that semantic network analysis allows for the characterization of differences in conceptual organization among students using active learning methodologies, serving as a complementary tool for assessing meaningful learning in Microbiology.

scientific communication and education↗

bioRxiv2020

Operative and technical modifications to the Coriolis(R) μ air sampler that improve sample recovery and biosafety during microbiological air sampling

Detecting infectious aerosols is central for gauging and countering airborne threats. In this regard the Coriolis(R) {micro} cyclonic air sampler is a practical, commercial collector that can be used with various analysis methods to monitor pathogens in air. However, information on how to operate this unit under optimal sampling and biosafety conditions is limited. We investigated Coriolis performance in aerosol dispersal experiments with polystyrene microspheres and Bacillus globigii spores. We report inconsistent sample recovery from the collector cone due to loss of material when sampling continuously for more than 30 min. Introducing a new collector cone every 10 min improved this shortcoming. Moreover, we found that several surfaces on the device become contaminated during sampling. Adapting a HEPA-filter system to the Coriolis prevented contamination without altering collection efficiency or tactical deployment. A Coriolis modified with these operative and technical improvements was used to collect aerosols carrying microspheres released inside a Biosafety Level-3 laboratory during simulations of microbiological spills and aerosol dispersals. In summary, we provide operative and technical solutions to the Coriolis that optimize microbiological air sampling and improve biosafety.

microbiology↗

bioRxiv2020

Microbiological water quality of Managed Aquifer Recharge systems in the salinity-prone southwest coastal Bangladesh

Managed aquifer recharge (MAR), a hydro-geological intervention designed to dilute groundwater salinity, pumps pond water treated through a slow sand filter into the underground aquifers. We evaluated the microbiological safety of the resulting MAR water at sites from three districts in southwest coastal Bangladesh. We collected monthly paired pond-MAR water samples from July 2016-June 2017 and enumerated fecal coliforms and E. coli using the IDEXX quanti-tray technique, by the most probable number (MPN) method. We used WHO risk categories for microbiological quality; no risk (<1 MPN), low risk (1-10 MPN) and moderate to high risk (>10 MPN per 100 mL water). We estimated the difference in mean log10 MPN in pond and MAR water using linear mixed effect models with random intercepts and cluster adjusted robust standard error. Almost all pond water samples (292/299, 98%) had moderate- to high-risk level (>10 MPN) fecal coliforms and E. coli (283/299, 95%). In contrast, 81% (242/300) of MAR water samples had no or low risk level fecal coliforms (0-10 MPN), of which 60% (179/300) had no fecal coliforms. We detected no or low risk level E. coli in 94% (283/300) of MAR water samples of these 80% (240/300) had no E. coli. MAR samples had lower mean log10 MPN fecal coliforms (-2.37; 95% CI: -2.56, -2.19) and E. coli (-2.26; 95% CI: - 2.43, -2.09) than pond water; microbial reductions remained consistent during the wet (May-October) and dry seasons. MAR-systems provided water with reduced fecal indicator bacteria compared to infiltered pond water.

microbiology↗

bioRxiv2022

The Composition of Diesel Fuel Influences the Structure of Microbiological Assemblages in Contaminated Fuel Storage Tanks

Microbiological contamination in diesel storage tanks is widespread and under-reported. The contaminating microorganisms can degrade components of the fuel, which contributes to fouling and corrosion. To better understand the connection between the microorganisms that are responsible for this contamination, the composition of affected fuels, and the resulting impact on fuel quality, we conducted a survey of 106 fuel tanks at 17 military bases across the continental United States. Fuel was sampled from each tank and the resident microbial communities were characterized using high throughput sequencing of small subunit ribosomal RNA gene libraries. Fatty acid methyl esters (FAME) and n-alkanes were characterized and quantified using GC-MS to determine their correlation with the presence of microbial taxa. Redundancy Analyses identified which microbial taxa were more prominent in contaminated fuels. Members of the fungal family Trichomaceae were found to be prominent in fuels containing more FAME. Members of the yeast family Debaryomycetaceae were found to be prominent in fuels containing more pentadecanoic and oleic acid methyl esters. These relationships between fungal taxa and fuel components were directly tested in growth experiments with representative isolates of the Trichocomaceae (Paecilomyces AF001) and Debaryomycetaceae (Wickerhamomyces SE3) families. Paecilomyces was capable of growth on linoleic acid methyl ester but unable to grow on pentadecanoic acid methyl ester, while Wickerhamomyces was able to grow on both substrates. Fuel composition may provide some insight into which microorganisms can proliferate but other factors like competition and symbiosis may also drive microbial proliferation, fouling, degradation, and corrosion in diesel fuels. ImportanceBiodiesel, widely used as an additive or extender of ultra-low sulfur diesel, can increase the potential for microorganisms to proliferate in storage tanks. It is important to know how the composition of diesel fuels can influence the growth of organisms linked to fuel degradation and microbiologically influenced corrosion. This research describes how certain populations of fungi and bacteria can prevail in fuels of different composition, which can be helpful in predicting biodegradation and biocorrosion, and formulating fuels less susceptible to the growth of problematic organisms.

microbiology↗