Biology subjects

Colwell, R. R.

Publications and source records attributed to Colwell, R. R..

9 recordsLinked to original sources

bioRxiv2026

Microbial Community Multi-omic Analysis of Marsh Sediment post Crustacean Shell Compost Enrichment: pathogen emergence and community response

Changes in nutrient availability can rapidly alter microbial processes in natural environments, with implications in biogeochemical cycling and pathogen emergence. Short-term, functional responses of microbial communities to nutrient amendment in coastal communities remain poorly understood, particularly in temperate environments. A 48-hour microcosm pulse experiment was completed in which paired metagenomic and metatranscriptomic sequencing were employed to examine how the decomposition of chitin rich substrates, namely crab and lobster shell compost, alters salt marsh microbiome structure and function. Within 48 hours of amendment, pronounced shifts in community metabolism were observed, including increased chitin degradation and utilization, stress-response, and sporulation. These responses coincided with marked decreases in genes associated with key biogeochemical processes, including carbon fixation, sulfur oxidation and reduction, and other metabolic pathways. Shell compost addition also enriched putative pathogens and virulence-associated genes, accompanied by modest transcriptional activation, notably aerolysin A (aerA), which encodes the pore-forming exotoxin aerolysin. These results demonstrate temperate salt marsh sediment microbiomes can undergo shifts in community composition and function that is associated with chitin-rich nutrient perturbation. The sensitivity of temperate coastal systems to organic matter input and the potential for ecological and public-health relevant outcomes are underscored, notably given that chitin is among the most abundant and readily available bionutrients in aquatic ecosystems globally.

microbiology↗

bioRxiv2025

A Bait-and-Switch strategy links phenotypes to genes coding for Polymer-Degrading Enzymes in Intact Microbiomes

Advances in next generation sequencing have made it possible to explore microbial community dynamics and regulation of functionally important genes through metagenomics and metatranscriptomics. However, the use of meta-omics to link enzyme function directly with complex, community-level phenotypes remain largely unexplored. To overcome this gap, we developed a novel framework that integrates ecological concepts by microbial community perturbation with association analysis to a targeted phenotype. Specifically, we introduce a hypothesis-free "bait and switch" strategy demonstrated through salt marsh soil microcosm pulse experiments to detect and characterize novel enzymes responsible for chitin degradation. Soil microbial communities were "baited" with shell compost, a chitin-rich substrate, to trigger community succession toward chitin degraders and gene upregulation of chitinases. A "switch" was then employed, by addition of glucose, inducing rapid downregulation of genes putatively responsible for chitin degradation. Results demonstrate the feasibility of this approach to identify functionally important enzymes, in this example, 48 hours after chitin addition. The bait and switch community perturbation provides a framework for discovery of polymer degrading enzymes present in complex microbial communities and serves as a proof of concept applicable for linking enzyme function with emergent community level phenotypes.

microbiology↗

bioRxiv2024

Yanomami skin microbiome complexity challenges prevailing concepts of healthy skin.

The adult skin microbiome contributes to skin homeostasis and generally comprises relatively low microbial complexity, especially sebaceous sites, where lipophilic Cutibacterium and Malassezia spp. predominate. Current understanding of the healthy skin microbiome derives predominantly from studies of western, industrialized populations, with limited representation of diverse cultures and lifestyles. In this study, the skin microbiome of a remote indigenous Yanomami community was investigated, revealing a complex microbial community comprised of 115 novel bacterial genomes. The bacterial community composition included genera common to western skin microbiota and additional diverse taxa, which formed multiplex interactions with a dominant eukaryote, Malassezia globosa. Metatranscriptome-derived functional attributes of the microbial communities contributed to skin homeostasis, fortifying barrier integrity via lipid metabolism and acid production and protecting against oxidative stress. The Yanomami skin microbiome comprised a suite of microbial taxa co-detected within their various surroundings. Longitudinal monitoring of Western expeditioner microbiome revealed acquisition of the Yanomami skin microbiome following immersion into the Amazon and subsequent loss upon return to an industrialized setting. These findings challenge the prevailing Western-centric view of what comprises a healthy adult skin microbiome, suggesting a diverse community that includes bacteria of environmental origin confers benefits not recognized in the current model of healthy skin. Importantly, we highlight the malleability of adult skin microbiome composition, which includes changes sustained by lifestyle modification.

microbiology↗

bioRxiv2023

Persistent effects of intramammary ceftiofur treatment on the gut microbiome and antibiotic resistance in dairy cattle

Intramammary (IMM) ceftiofur treatment is commonly used in dairy farms to prevent mastitis, though its impact on the cattle gut microbiome and selection of antibiotic-resistant bacteria has not been elucidated. Herein, we enrolled 40 healthy dairy cows after lactation: 20 were treated with IMM ceftiofur (Spectramast(R)DC) and a non-antibiotic internal teat sealant (bismuth subnitrate) and 20 (controls) received only bismuth subnitrate. Fecal samples were collected before (day -1) and after treatment (weeks 1, 2, 3, 5, 7, and 9) for bacterial quantification and metagenomic next-generation sequencing. Overall, 90% and 24% of the 278 samples had Gram-negative bacteria with resistance to ampicillin and ceftiofur, respectively. Most of the cows treated with ceftiofur did not have an increase in the number of resistant bacteria; however, a subset (25%) shed higher levels of ceftiofur-resistant bacteria for up to 2 weeks post-treatment. At week 5, the antibiotic-treated cows had lower microbiome abundance and richness, whereas a greater abundance of genes encoding extended-spectrum {beta}-lactamases (ESBLs), CfxA, ACI-1, and CMY, was observed at weeks 1, 5 and 9. Moreover, the contig and network analyses detected associations between {beta}-lactam resistance genes and phages, mobile genetic elements, and specific genera. Commensal bacterial populations belonging to Bacteroidetes most often possessed ESBL genes followed by members of Enterobacteriaceae. This study highlights variable, persistent effects of IMM ceftiofur treatment on the gut microbiome and resistome in dairy cattle. Antibiotic-treated cattle had an increased abundance of specific taxa and genes encoding ESBL production that persisted for 9 weeks, while fecal shedding of ESBL-producing Enterobacteriaceae varied across animals. Together, these findings highlight the need for additional studies that identify factors linked to shedding levels and the dissemination and persistence of resistance determinants on dairy farms in different geographic locations.

microbiology↗

bioRxiv2021

Prior exposure to microcystin alters host gut resistome and is associated with dysregulated immune homeostasis in translatable mouse models

The increased propensity of harmful algal blooms (HABs) and exposure from HABs-cyanotoxin causes human toxicity. It has been associated with the progression of several diseases that encompass the liver, kidneys, and immune system. Recently, a strong association of cyano-HAB toxicity with the altered host gut microbiome has been shown. We tested the hypothesis that prior exposure to cyanotoxin microcystin may alter the microbiome and induce microbiome-host-resistome crosstalk. Using both wild-type and humanized mice, we show that the mice exposed to microcystin had an altered microbiome signature that harbored antimicrobial resistance genes. Host resistome phenotypes such as mefA, msrD, mel, ant6, and tet40 increased in diversity and relative abundance following microcystin exposure. Interestingly, the increased abundance of these genes was traced to resistance to common antibiotics such as tetracycline, macrolides, glycopeptide, and aminoglycosides, crucial for modern-day treatment for several diseases. Increased abundance of these genes was positively associated with increased expression of PD1, a T-cell homeostasis marker, and pleiotropic inflammatory cytokine IL-6 with a concomitant negative association with immunosurveillance markers IL7 and TLR2. Microcystin exposure also caused decreased TLR2, TLR4, and REG3G expressions, increased immunosenescence, and higher systemic levels of IL-6 in both wild-type and humanized mice. In conclusion, the results show a first-ever characterization of the host resistome of microcystin exposure and its connection to host immune status and antibiotic resistance. The results may be crucial for understanding the ability of exposed subjects to fight future bacterial infections and the progression of the debilitating disease in hospital settings.

microbiology↗

bioRxiv2021

Genomic characteristics of recently recognized Vibrio cholerae El Tor lineages associated with cholera in Bangladesh, 1991-2017

Comparative genomic analysis of Vibrio cholerae El Tor associated with endemic cholera in Asia revealed two distinct lineages, one dominant in Bangladesh and the other in India. An in depth whole genome study of V. cholerae El Tor clinical strains isolated during endemic cholera in Bangladesh (1991 - 2017) included reference genome sequence data obtained online. Core genome phylogeny established using single nucleotide polymorphisms (SNPs) showed V. cholerae El Tor strains comprised two lineages, BD-1 and BD-2, which, according to Bayesian phylodynamic analysis, originated from paraphyletic group BD-0 around 1981. BD-1 and BD-2 lineages overlapped temporally but were negatively associated as causative agents of cholera 2004-2017. Genome wide association study (GWAS) revealed 140 SNPs and 31 indels, resulting in gene alleles unique to BD-1 and BD-2. Regression analysis of root to tip distance and year of isolation indicated early BD-0 strains at the base, whereas BD-1 and BD-2 subsequently emerged and progressed by accumulating SNPs. Pangenome analysis provided evidence of gene acquisition by both BD-1 and BD-2, of which six crucial proteins of known function were predominant in BD-2. BD-1 and BD-2 diverged and have distinctively different genomic traits, namely heterogeneity in VSP-2, VPI-1, mobile elements, toxin encoding elements, and total gene abundance. In addition, the observed phage-inducible chromosomal island-like element (PLE1), and SXT ICE elements (ICETET) in BD-2 presumably provided a fitness advantage for the lineage to outcompete BD-1 as the etiological agent of the endemic cholera in Bangladesh, with implications for global cholera epidemiology. ImportanceCholera is a global disease with specific reference to the Bay of Bengal Ganges Delta where Vibrio cholerae O1 El Tor, causative agent of the disease showed two circulating lineages, one dominant in Bangladesh and the other in India. Results of in-depth genomic study of V. cholerae associated with endemic cholera during the past 27 years (1991 - 2017) indicate emergence and succession of the two lineages, BD-1 and BD-2, arising from a common ancestral paraphylatic group, BD-0, comprising the early strains and short-term evolution of the bacterium in Bangladesh. Among the two V. cholerae lineages, BD-2 supersedes BD-1 and is predominant in the most recent endemic cholera in Bangladesh. The BD-2 lineage contained significantly more SNPs and indels, and showed richness in gene abundance, including antimicrobial resistance genes, gene cassettes, and PLE to fight against bacteriophage infection, acquired over time. These findings have important epidemic implications at a global scale.

genomics↗

bioRxiv2021

Vibrio cholerae El Tor strains linked to global cholera are homogeneous by pulsed-field gel electrophoresis

Vibrio cholerae O1 El Tor, causative agent of the ongoing seventh cholera pandemic, is native to the aquatic environment of the Ganges Delta, Bay of Bengal (GDBB). Recent studies traced pandemic strains to the GDBB and proposed global spread of cholera had occurred via intercontinental transmission. In the research presented here, NotI-digested genomic DNA extracted from V. cholerae O1 clinical and environmental strains isolated in Bangladesh during 2004 - 2014 was analyzed by pulsed-field gel electrophoresis (PFGE). Results of cluster analysis showed 94.67% of the V. cholerae isolates belonged to clade A and included the majority of clinical isolates of spatio-temporal origin and representing different cholera endemic foci. The rest of the strains were estuarine, all environmental isolates from Mathbaria, Bangladesh, and occurred as singletons, clustered in clades B and C, or in the small clades D and E. Cluster analysis of the Bangladeshi strains and including 157 El Tor strains from thirteen countries in Asia, Africa, and the Americas revealed 85% of the total set of isolates belonged to clade A, indicating all were related, yet did not form an homogeneous cluster. Overall, 15% of the global strains comprised multiple small clades or segregated as singletons. Three sub-clades could be discerned within the major clade A, reflecting distinct lineages of V. cholerae El Tor associated with cholera in Asia, Africa, and the Americas. The presence in Asia and the Americas of non-pandemic V. cholerae El Tor populations differing by PFGE and from strains associated with cholera globally suggests different ecotypes are resident in distant geographies. Author SummaryCholera is a major health threat, especially in the Ganges Delta, Bay of Bengal (GDBB). Vibrio cholerae, causative agent of cholera, is native to the GDBB aquatic environment. Recent genomic studies suggest GDBB is the cholera hotspot where the disease spreads globally via human activity. Pulsed-field gel electrophoresis (PFGE) of NotI-digested genomic DNA from V. cholerae El Tor endemic cholera strains was done, including Bangladesh aquatic environment and clinical strains from distant geographical regions representing three cholera-prone continents. Results showed the majority of pandemic strains belonged to a major cluster, suggesting clonal relatedness. Ecotypes were detected, indicating geographically specific lineages. It is concluded that epidemic strains in Bangladesh and thirteen countries of Asia, Africa, and the Americas are geographically adapted, with independent evolution of the bacterium in respective geographical regions.

molecular biology↗

bioRxiv2021

Large scale genomic and evolutionary study reveals SARS-CoV-2 virus isolates from Bangladesh strongly correlate with European origin and not with China.

RationaleThe global public health is in serious crisis due to emergence of SARS-CoV-2 virus. Studies are ongoing to reveal the genomic variants of the virus circulating in various parts of the world. However, data generated from low- and middle-income countries are scarce due to resource limitation. This study was focused to perform whole genome sequencing of 151 SARS-CoV-2 isolates from COVID-19 positive Bangladeshi patients. The goal of this study was to identify the genomic variants among the SARS-CoV-2 virus isolates in Bangladesh, to determine the molecular epidemiology and to develop a relationship between host clinical trait with the virus genomic variants. MethodSuspected patients were tested for COVID-19 using one step commercial qPCR kit for SARS-CoV-2 Virus. Viral RNA was extracted from positive patients, converted to cDNA which was amplified using Ion AmpliSeq SARS-CoV-2 Research Panel. Massive parallel sequencing was carried out using Ion AmpliSeq Library Kit Plus. Assembly of raw data is done by aligning the reads to a pre-defined reference genome (NC_045512.2) while retaining the unique variations of the input raw data by creating a consensus genome. A random forest-based association analysis was carried out to correlate the viral genomic variants with the clinical traits present in the host. ResultAmong the 151 viral isolates, we observed the 413 unique variants. Among these 8 variants occurred in more than 80 % of cases which include 241C to T, 1163A to T, 3037C to T,14408C to T, 23403A to G, 28881G to A, 28882 G to A, and finally the 28883G to C. Phylogenetic analysis revealed a predominance of variants belonging to GR clade, which have a strong geographical presence in Europe, indicating possible introduction of the SARS-CoV-2 virus into Bangladesh through a European channel. However, other possibilities like a route of entry from China cannot be ruled out as viral isolate belonging to L clade with a close relationship to Wuhan reference genome was also detected. We observed a total of 37 genomic variants to be strongly associated with clinical symptoms such as fever, sore throat, overall symptomatic status, etc. (Fishers Exact Test p-value<0.05). The most mention-worthy among those were the 3916CtoT (associated with causing sore throat, p-value 0.0005), the 14408C to T (associated with protection from developing cough, p-value= 0.027), and the 28881G to A, 28882G to A, and 28883G to C variant (associated with causing chest pain, p-value 0.025). ConclusionTo our knowledge, this study is the first large scale phylogenomic studies of SARS-CoV-2 virus circulating in Bangladesh. The observed epidemiological and genomic features may inform future research platform for disease management, vaccine development and epidemiological study.

genetics↗

bioRxiv2017

Metagenomic sequencing to replace semi-quantitative urine culture for detection of urinary tract infections: a proof of concept

ABSTRACTSemi-quantitative bacterial culture is the standard method to diagnose urinary tract infections (UTI), but bacterial growth rate limits diagnostic speed and it is unreliable when patients have been pre-treated with antibiotics. Metagenomics could increase diagnostic speed and accuracy by sequencing the microbiome and resistome directly from urine samples, bypassing culture. However, a semi-quantitative approach - as needed for diagnosing UTIs - has not been established.\n\nMetagenomics was deployed to identify and semi-quantify bacterial presence indicative of UTI, predict antimicrobial susceptibility (AMR), and results were compared to semi-quantitative culture. Whole genome sequencing of the corresponding uropathogens was done for comparison. Analysis time and cost were tracked.\n\nForty-one consecutive urine samples underwent metagenomic analysis. All culture positive samples contained >200ng of DNA, suggestive of a threshold below which UTI could be ruled out solely based on DNA quantity. A semi-quantitative Diagnostic Index (DI) was created by multiplying the total DNA quantity by the relative abundance of uropathogens per urine sample. The DI allowed discrimination of UTI from non-UTI samples in all but 1 case. Metagenomic detection of AMR determinants correctly predicted the phenotype of uropathogens in 20 of 32 cases. The metagenomic work-flow was 31h and cost {euro}116 per sample, but could be reduced to 4.5h and {euro}5 for low-DNA-yield non-UTI samples.\n\nThe genomic determinants of AMR and their distribution across uropathogens need to be better understood for prediction of AMR phenotypes by metagenomics. The introduction of the DI demonstrates the potential of semi-quantitative metagenomics to replace culture as rapid diagnostic method for UTI.

microbiology↗