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bioRxiv2017

Identification of Rab18 as an Essential Host Factor for BKPyV Infection Using a Whole Genome RNA Interference Screen

BK polyomavirus (BKPyV) is a human pathogen first isolated in 1971. BKPyV infection is ubiquitous in the human population, with over 80% of adults worldwide being seropositive for BKPyV. BKPyV infection is usually asymptomatic; however, BKPyV reactivation in immunosuppressed transplant patients causes two diseases, polyomavirus-associated nephropathy and hemorrhagic cystitis. To establish a successful infection in its host cells, BKPyV must travel in retrograde transport vesicles to reach the nuclei. To make this happen, BKPyV requires the cooperation of host cell proteins. To further identify host factors associated with BKPyV entry and intracellular trafficking, we performed a whole-genome siRNA screen on BKPyV infection of primary human renal proximal tubular epithelial cells. The results revealed the importance of the Ras-related protein Rab18 and syntaxin 18 for BKPyV infection. Our subsequent experiments implicated additional factors that interact with this pathway, and suggest a more detailed model of the intracellular trafficking process, indicating that BKPyV reaches the ER lumen through a retrograde transport pathway between the late endosome and the ER.

microbiology↗

bioRxiv2017

Obstruction of pilus retraction stimulates bacterial surface sensing

Surface association provides numerous fitness advantages to bacteria. Thus, it is critical for bacteria to recognize surface contact and to consequently initiate physiological changes required for a surface-associated lifestyle (1). Ubiquitous microbial appendages called pili are involved in sensing surfaces and mediating downstream surface-associated behaviors (2-6). The mechanism by which pili mediate surface sensing remains unknown, largely due to the difficulty to visualize their dynamic nature and to directly modulate their activity without genetic modification. Here, we show that Caulobacter crescentus pili undergo dynamic cycles of extension and retraction that cease within seconds of surface contact, and this arrest of pilus activity coincides with surface-stimulated holdfast synthesis. By physically blocking pili, we show that imposing resistance to pilus retraction is sufficient to stimulate holdfast synthesis in the absence of surface contact. Thus, resistance to type IV pilus retraction upon surface attachment is used for surface sensing.\n\nOne Sentence SummaryBacteria use the tension imparted on retracting pilus fibers upon their binding to a surface for surface sensing.

microbiology↗

bioRxiv2017

Two phosphoglucomutase paralogs regulate triggered secretion of the Toxoplasma micronemes

Parafusin is a phosphoglucomutase (PGM) paralog that acts as a signaling scaffold protein in calcium mediated exocytosis across many eukaryotes. In Toxoplasma gondii the parafusin related protein 1 (PRP1) has been associated in indirect and heterologous studies with the regulated exocytosis of the micronemes, which are required for successful host cell invasion and egress. Here we directly assessed the role of PRP1 by deleting the gene from the parasite. We observed a specific defect in microneme secretion in response to high Ca2+ fluxes, but not to phosphatidic acid fluxes controlling microneme release. We observed no defect in constitutive microneme secretion which was sufficient to support completion of the lytic cycle. Furthermore, deletion of the other PGM in Toxoplasma, PGM2, as well as the double PRP1/PGM2 deletion resulted in a similar phenotype. This suggests a functional interaction between these two genes. Strikingly, tachyzoites without both paralogs are completely viable in vitro and during acute mice infections. This indicates that PGM activity is neither required for glycolysis. In conclusion, the PRP1-PGM2 pair is required for a burst in microneme secretion upon high Ca2+ fluxes, but this burst is not essential to complete the lytic cycle of the parasite.\n\nPlain Language SummaryCalcium mediated control of microneme secretion is essential for host cell invasion and egress of Toxoplasma gondii. Here it is shown that the two phosphoglucomutases in Toxoplasma both function in the translation of a spike in calcium into a burst in microneme secretion.

microbiology↗

bioRxiv2017

Nonpolio enteroviruses can also be recovered from non-reproducible cytopathology in L20B cell line.

Samples showing cytopathology (CPE) on initial inoculation into L20B cell line but with no observed or reproducible CPE on passage in L20B or RD are considered negative for both poliovirus and nonpolio enteroviruses (NPEVs). The phenomenon is termed non-reproducible CPE. Its occurrence is usually ascribed to the likely presence of reoviruses, adenoviruses and other non-enteroviruses. This study aimed to investigate the likelihood that NPEVs are also present in cases with non-reproducible CPE.\n\nTwenty-six (26) cell culture suspensions were analyzed in this study. The suspensions were collected from the WHO National Polio Laboratory, Department of Virology, College of Medicine, University of Ibadan. The suspensions emanated from 13 L20B cell culture tubes that showed cytopathology within 5 days of inoculation with fecal suspension from AFP cases. However, on passage into one each of RD and L20B cell lines, the CPE was not reproducible. All samples were subjected to RNA extraction, cDNA synthesis, the WHO recommended VP1 RT-seminestedPCR assay, species resolution PCR assay, sequencing and phylogenetic analysis.\n\nSix (6) samples were positive for the VP1 RT-seminested PCR assay. Only four of which were positive by the species resolution PCR assay. The four amplicons were sequenced, however, only three (3) were successfully identified as Coxsackievirus A20 (2 isolates) and Echovirus 29 (1 isolate).\n\nThe results of this study unambiguously showed the presence of NPEVs (particularly CVA20 and E29) in cell culture supernatants of samples with CPE on initial inoculation into L20B cell line but with no observed or reproducible CPE on passage in RD cell line. Therefore, like reoviruses, adenoviruses and other non-enteroviruses, NPEVs can also be recovered in cases with non-reproducible CPE.

microbiology↗

bioRxiv2017

Mechanisms of surface antigenic variation in the human pathogenic fungus Pneumocystis jirovecii

Microbial pathogens commonly escape the human immune system by varying surface proteins. We investigated the mechanisms used for that purpose by Pneumocystis jirovecii. This uncultivable fungus is an obligate pulmonary pathogen which causes pneumonia in immuno-compromised individuals, a major life-threatening infection. Long-read PacBio sequencing was used to assemble a core of subtelomeres of a single P. jirovecii strain from a bronchoalveolar lavage fluid specimen of a single patient. A total of 113 genes encoding surface proteins were identified, including 28 pseudogenes. These genes formed a subtelomeric gene superfamily which included five families encoding adhesive GPI-anchored glycoproteins, and one family encoding excreted glycoproteins. Numerical analyses suggested that diversification of the glycoproteins relies on mosaic genes created by ectopic recombination, and occurs only within each family. DNA motifs suggested that all genes are expressed independently, except those of the family encoding the most abundant surface glycoproteins which are subject to mutually exclusive expression. PCR analyses showed that exchange of the expressed gene of the latter family occurs frequently, possibly favoured by the location of the genes proximal to the telomere because this allows concomitant telomere exchange. Our observations suggest that (i) P. jirovecii cell surface is made of a complex mixture of different surface proteins, with a majority of a single isoform of the most abundant glycoprotein, (ii) genetic mosaicism within each family ensures variation of the glycoproteins, and (iii) the strategy of the fungus consists in the continuous production of new subpopulations composed of cells which are antigenically different.

microbiology↗

bioRxiv2017

MCE domain proteins: conserved inner membrane lipid-binding proteins required for outer membrane homeostasis

Bacterial proteins with MCE domains were first described as being important for Mammalian Cell Entry. More recent evidence suggests they are components of lipid ABC transporters. In Escherichia coli, the single-domain protein MlaD is known to be part of an inner membrane transporter that is important for maintenance of outer membrane lipid asymmetry. Here we describe two multi MCE domain-containing proteins in Escherichia coli, PqiB and YebT, the latter of which is an orthologue of MAM-7 that was previously reported to be an outer membrane protein. We show that all three MCE domain-containing proteins localise to the inner membrane. Bioinformatic analyses revealed that MCE domains are widely distributed across bacterial phyla but multi MCE domain-containing proteins evolved in Proteobacteria from single-domain proteins. Mutants defective in mlaD, pqiAB and yebST were shown to have distinct but partially overlapping phenotypes, but the primary functions of PqiB and YebT differ from MlaD. Complementing our previous findings that all three proteins bind phospholipids, results presented here indicate that multi-domain proteins evolved in Proteobacteria for specific functions in maintaining cell envelope homeostasis.

microbiology↗

bioRxiv2017

Small subsets of highly connected taxa predict compositional change in microbial communities

For decades, ecological theory has predicted that the complexity of communities should be related to their stability. However, this prediction has rarely been tested empirically, because of both the difficulty of finding suitable systems where the question is tractable and the trouble of defining \"stability\" in real systems. Microbial communities provide the opportunity to investigate a related question: how does community connectivity relate to the rate of compositional turnover? We used a newly developed metric called community \"cohesion\" to test how microbial community connectivity relates to Bray-Curtis dissimilarity through time. In three long-term datasets, we found that stronger connectivity corresponded to lower rates of compositional turnover. Using two case studies of disturbed and reference communities, we found that the predictive power of community connectivity was diminished by external disturbance. Finally, we tested whether the highly connected taxa were disproportionately important in explaining compositional turnover. We found that subsets of highly connected \"keystone\" taxa, generally comprising 1-5% of community richness, explained community turnover better than using all taxa. Our results suggest that stronger biotic interactions within microbial community dynamics are stabilizing to community composition, and that highly connected taxa are good indicators of pending community shifts.

microbiology↗

bioRxiv2017

Mapping-based all-RNA-information sequencing analysis (ARIseq) pipeline simultaneously revealed taxonomic composition, gene expression, and their correlation in an acidic stream ecosystem

We developed a new pipeline for simultaneous analyses of both rRNA profile as a taxonomic marker and mRNA profile as a functional marker, to understand microbial ecosystems in natural environments. Our pipeline, named All-RNA-Information sequencing (ARIseq), comprises a high-throughput sequencing of reverse transcribed total RNA and several widely used computational tools, and generates quantitatively reliable information on both community structures and gene expression patterns, which were verified by quantitative PCR analyses in this study. Particularly, correlation network analysis in the pipeline can reveal microbial taxa and expressed genes that share patterns of dynamics among different time and/or geographical points. The pipeline is primarily mapping-based, using a public database for small subunit rRNA genes and obtained contigs as the reference database for protein-coding genes. We applied this pipeline to biofilm samples, as examples, collected from an acidic spring water stream in the Chyatsubomi-goke Park in Gunma prefecture, Japan. Our analyses revealed the predominance of iron and sulfur-oxidizing bacteria and Pinnularia diatoms, and also indicated that the distributions of the iron-sulfur-oxidizing bacterial consortium and the Pinnularia diatoms largely overlapped but showed distinct patterns. In addition, our analyses showed that the iron-oxidizing bacterial genus Acidithiobacillus and co-occurring Acidiphilium shared similar distribution pattern whereas another iron-oxidizing genus Leptospirillum exhibited a distinct pattern. Our pipeline enables researchers to more easily capture the outline of microbial ecosystems based on the taxonomic composition, protein-coding gene expression, and their correlations.

microbiology↗

bioRxiv2017

SParticle, an algorithm for the analysis of filamentous microorganisms in submerged cultures

Streptomycetes are filamentous bacteria that produce a plethora of bioactive natural products and industrial enzymes. Their mycelial lifestyle typically results in high heterogeneity in bioreactors, with morphologies ranging from fragments and open mycelial mats to dense pellets. There is a strong correlation between morphology and production in submerged cultures, with small and open mycelia favoring enzyme production, while most antibiotics are produced mainly in pellets. Here we describe SParticle, a Streptomyces Particle analysis method that combines whole slide imaging with automated image analysis to characterize the morphology of submerged grown Streptomyces cultures. SParticle allows the analysis of over a thousand particles per hour, offering a high throughput method for the imaging and statistical analysis of mycelial morphologies. The software is available as a plugin for the open source software ImageJ and allows users to create custom filters for other microbes. Therefore, SParticle is a widely applicable tool for the analysis of filamentous microorganisms in submerged cultures.

microbiology↗

bioRxiv2017

Reactive Oxygen Species-Dependent Essential Genes in Salmonella Typhimurium

BackgroundThe molecular mechanisms underlying bacterial cell death due to stresses or bactericidal antibiotics are complex and remain puzzling. Previously, it was shown that iron is required for effective killing of bacterial cells by numerous bactericidal antibiotics. Here, our high-resolution Tn-seq analysis demonstrated that transposon mutants of S. Typhimurium with insertions in essential genes escaped immediate killing or growth inhibition under iron-restricted conditions for approximately one-third of all essential genes.\n\nResultsWe grouped essential genes into two categories, iron-dependent and iron-independent essential genes. The iron-dependency of the iron-dependent essential genes was further validated by the fact that the relative abundance of these essential gene mutants increased further with more severe iron restrictions. Our unexpected observation can be explained well by the recently proposed common killing mechanisms of bactericidal antibiotics via production of reactive oxygen species (ROS). In this model iron restriction would inhibit production of ROS, leading to reduced killing activity following blocking of an essential function. Interestingly, the targets of most antibiotics currently in use clinically, whether bacteriostatic or bactericidal, are iron-dependent essential genes.\n\nConclusionsOur result suggests that targeting iron-independent essential genes may be a better strategy for future antibiotic development, because blocking these genes would lead to immediate cell death regardless of iron concentration. On the contrary, blocking iron-dependent pathways under iron limited in vivo environment could lead to reduced killing action, which might increase drug-resistance by mutagenic action of sublethal concentrations of ROS. This work expands our knowledge on the role of iron to a broader range of essential pathways, and provides novel insights for development of more effective antibiotics.

microbiology↗

bioRxiv2017

Detection and antibiotic susceptibility of pathogenic Escherichia coli isolated from the final effluent of two wastewater treatment plants in the Eastern Cape Province of South Africa

Wastewater is an important reservoir for Escherichia coli and can present significant acute toxicity if released into receiving water sources without being adequately treated. To analyze whether pathogenic E. coli strains that cause infections are in treated effluent and to recognize antibiotic profile. 476 confirmed isolates from two treatment Plants were characterized for the presence of various E. coli pathotypes. A total of 8 pathotypes were screened and only four were confirmed. UPEC was about 5.7% followed by EAEC at 2.3%, NMEC at 1.1% and EPEC at 0.6%. Antibiotic susceptibility patterns of E. coli pathotypes such as UPEC showed low resistance to antibiotics like meropenem (100%), cefotaxime (100%) and gentamicin (88.9%). The pathotype also showed high degrees of resistance to tetracycline (74.1%), ampicillin (74.1%) and cephalothin (66.7%). Other E. coli pathotypes, EAEC, NMEC and EPEC, showed high sensitivity (100%) to meropenem, gentamicin and cefotaxime, and varying degree of resistances to ampicillin, tetracycline and cephalothin. The results of this study reveal that the two Plants discharge effluents with pathogenic E. coli and are reservoir for the bacteria into receiving water sources. In summary, this finding raises the possibility that at least some pathogenic E. coli pathotypes are getting into the environment through WWTPs and represent potential route for enteropathogenic infection. In addition, certain pathotypes may have acquired resistance properties, becoming a potential cause of drug resistance infection. This study reveals inadequacy of the plants studied to produce effluents of acceptable quality.

microbiology↗

bioRxiv2017

Rapid, parallel identification of pathways for catabolism of lignin-derived aromatic compounds

This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).

microbiology↗

bioRxiv2017

Maize Phyllosphere Microbial Community Niche Development Across Stages of Host Leaf Growth

The phyllosphere hosts a variety of microorganisms, including bacteria, which can play a positive role in the success of the host plant. Bacterial communities in the phylloplane are influenced by both biotic and abiotic factors, including host plant surface topography and chemistry, which change in concert with microbial communities as the plant leaves develop and age. We examined how Zea mays leaf microbial community structure changed with plant age. Ribosomal spacer length (ARISA) and scanning electron microscopic (size trait) imaging strategies were used to assess microbial community composition across maize plant ages, using a novel staggered experimental design. Significant changes in community composition were observed for both molecular and imaging analyses, and the two analysis methods provided complementary information about bacterial community structure within each leaf developmental stage. Both taxonomic and cell-size trait patterns provided evidence for niche-based contributions to microbial community development on leaves.

microbiology↗

bioRxiv2017

Cyanobacterial Growth on Municipal Wastewater Requires Low Temperatures

Side-streams in wastewater treatment plants can serve as concentrated sources of nutrients (i.e. nitrogen and phosphorus) to support the growth of photosynthetic organisms that ultimately serve as feedstock for production of fuels and chemicals. However, other chemical characteristics of these streams may inhibit growth in unanticipated ways. Here, we evaluated the use of liquid recovered from municipal anaerobic digesters via gravity belt filtration as a nutrient source for growing the cyanobacterium Synechococcus sp. strain PCC 7002. The gravity belt filtrate (GBF) contained high levels of complex dissolved organic matter (DOM), which seemed to negatively influence cells. We investigated the impact of GBF on physiological parameters such as growth rate, membrane integrity, membrane composition, photosystem composition, and oxygen evolution from photosystem II. At 37{degrees}C, we observed an inverse correlation between GBF concentration and membrane integrity. Radical production was also detected upon exposure to GBF at 37{degrees}C. However, at 27{degrees}C the dose dependent relationship between GBF concentration and lack of membrane integrity was abolished. Immediate resuspension of strains in high doses of GBF showed markedly reduced oxygen evolution rates relative to the control. Together, this suggests that one mechanism responsible for GBF toxicity to Synechococcus is the interruption of photosynthetic electron flow and subsequent phenomena. We hypothesize this is likely due to the presence of phenolic compounds within the DOM.\n\nIMPORTANCECyanobacteria are viewed as promising platforms to produce fuels and/or high-value chemicals as part of so-called \"bio-refineries\". Their integration into wastewater treatment systems is particularly interesting because removal of the nitrogen and phosphorus in many wastewater streams is an expensive but necessary part of wastewater treatment. In this study, we evaluated strategies for cultivating Synechococcus strain PCC 7002 on media comprised of two wastewater streams; treated secondary effluent supplemented with the liquid fraction extracted from sludge following anaerobic digestion. This strain is commonly used for metabolic engineering to produce a variety of valuable chemical products and product precursors (e.g. lactate). However, initial attempts to grow PCC 7002 under otherwise standard conditions of light and temperature failed. We thus systematically evaluated alternative cultivation conditions and then used multiple methods to dissect the apparent toxicity of the media under standard cultivation conditions.

microbiology↗

bioRxiv2017

Characterising maize viruses associated with maize lethal necrosis symptoms in sub Saharan Africa

Maize lethal necrosis disease (MLN) is an emerging disease in East Africa caused by the introduction of Maize chlorotic mottle virus (MCMV). Recent activity seeking to limit spread of the disease is reliant on effective diagnostics. Traditional diagnostics applied on samples with typical field symptoms of MLN have often given negative results using ELISA or PCR for MCMV and Sugarcane mosaic virus (SCMV). Samples collected in the field with typical MLN symptoms were examined using next generation sequencing (NGS). SCMV was found to be more prevalent than suggested by targeted diagnostics. Additionally, the panel of samples were found to be infected with a range of other viruses, seven of which are described here for the first time. Although not previously identified in the region, Maize yellow mosaic virus (MYMV) was the most prevalent virus after MCMV. The development of targeted diagnostics for emerging viruses is complicated when the extent of field variation is unknown, something that can be negated by using NGS methods. As a result we explored MinION technology which may be more readily deployable in resource poor settings. The results show that this sequencer can diagnose known viruses and future iterations have the potential to identify novel viruses.

microbiology↗

bioRxiv2017

Gene flow between divergent cereal- and grass-specific lineages of the rice blast fungus Magnaporthe oryzae

Delineating species and epidemic lineages in fungal plant pathogens is critical to our understanding of disease emergence and the structure of fungal biodiversity, and also informs international regulatory decisions. Pyricularia oryzae (syn. Magnaporthe oryzae) is a multi-host pathogen that infects multiple grasses and cereals, is responsible for the most damaging rice disease (rice blast), and of growing concern due to the recent introduction of wheat blast to Bangladesh from South America. However, the genetic structure and evolutionary history of M. oryzae, including the possible existence of cryptic phylogenetic species, remain poorly defined. Here, we use whole-genome sequence information for 76 M. oryzae isolates sampled from 12 grass and cereal genera to infer the population structure of M. oryzae, and to reassess the species status of wheat-infecting populations of the fungus. Species recognition based on genealogical concordance, using published data or extracting previously-used loci from genome assemblies, failed to confirm a prior assignment of wheat blast isolates to a new species (Pyricularia graminis tritici). Inference of population subdivisions revealed multiple divergent lineages within M. oryzae, each preferentially associated with one host genus, suggesting incipient speciation following host shift or host range expansion. Analyses of gene flow, taking into account the possibility of incomplete lineage sorting, revealed that genetic exchanges have contributed to the makeup of multiple lineages within M. oryzae. These findings provide greater understanding of the eco-evolutionary factors that underlie the diversification of M. oryzae and highlight the practicality of genomic data for epidemiological surveillance in this important multi-host pathogen.\n\nImportanceInfection of novel hosts is a major route for disease emergence by pathogenic micro-organisms. Understanding the evolutionary history of multi-host pathogens is therefore important to better predict the likely spread and emergence of new diseases. Magnaporthe oryzae is a multi-host fungus that causes serious cereal diseases, including the devastating rice blast disease, and wheat blast, a cause of growing concern due to its recent spread from South America to Asia. Using whole genome analysis of 76 fungal strains from different hosts, we have documented the divergence of M. oryzae into numerous lineages, each infecting a limited number of host species. Our analyses provide evidence that inter-lineage gene flow has contributed to the genetic makeup of multiple M. oryzae lineages within the same species. Plant health surveillance is therefore warranted to safeguard against disease emergence in regions where multiple lineages of the fungus are in contact with one another.

microbiology↗

bioRxiv2017

Transcriptional responses of Escherichia coli during recovery from inorganic or organic mercury exposure

BackgroundThe protean chemical properties of mercury have long made it attractive for diverse applications, but its toxicity requires great care in its use, disposal, and recycling. Mercury occurs in multiple chemical forms, and the molecular basis for the distinct toxicity of its various forms is only partly understood. Global transcriptomics applied over time can reveal how a cell recognizes a toxicant and what cellular subsystems it marshals to repair and recover from the damage. The longitudinal effects on the transcriptome of exponential phase E. coli were compared during sub-acute exposure to mercuric chloride (HgCl2) or to phenylmercuric acetate (PMA) using RNA-Seq.\n\nResultsDifferential gene expression revealed common and distinct responses to the mercurials throughout recovery. Cultures exhibited growth stasis immediately after each mercurial exposure but returned to normal growth more quickly after PMA exposure than after HgCl2 exposure. Correspondingly, PMA rapidly elicited up-regulation of a large number of genes which continued for 30 min, whereas fewer genes were up-regulated early after HgCl2 exposure only some of which overlapped with PMA up-regulated genes. By 60 min gene expression in PMA-exposed cells was almost indistinguishable from unexposed cells, but HgCl2 exposed cells still had many differentially expressed genes. Relative expression of energy production and most metabolite uptake pathways declined with both compounds, but nearly all stress response systems were up-regulated by one or the other mercurial during recovery.\n\nConclusionsSub-acute exposure influenced expression of ~45% of all genes with many distinct responses for each compound, reflecting differential biochemical damage by each mercurial and the corresponding resources available for repair. This study is the first global, high-resolution view of the transcriptional responses to any common toxicant in a prokaryotic model system from exposure to recovery of active growth. The responses provoked by these two mercurials in this model bacterium also provide insights about how higher organisms may respond to these ubiquitous metal toxicants.

microbiology↗

bioRxiv2017

Investigating the occurrence of E. coli O157:H7 in the final effluents of two wastewater treatment plants

AIMThe final effluent of two wastewater plants located in the Eastern Cape of South Africa were tested for the presence of Enterohaemorrhagic Escherichia coli O157:H7 (E. coli O157:H7) isolates, and characteristics of the isolates obtained were determined.\n\nMETHODS AND RESULTSA total of 23 wastewater samples were collected from the treatment plants at the final effluent point after the disinfectant stages of wastewater processing. Altogether, 540 presumptive E. coli isolates were obtained by colony counting on the E. coli O157:H7 chromogenic agar base supplemented with cefixime tellurite and were sub-cultured onto sorbitol-MacConkey agar and tested for agglutination using the Prolex E. coli O157 latex test reagent kit. The results showed that the 149 suspected colonies from SMAC agar were all negative for the antisera.\n\nCONCLUSIONNone of the isolates agglutinated with antisera against E. coli O157. Thus no presence of the bacteria can be confirmed from the treated effluents\n\nSIGNIFICANCE AND IMPACT OF STUDYThe likelihood of the receiving water body and the environment being contaminated with E. coli O157:H7 is therefore minimal.

microbiology↗