Sulfite-reducing Bacteria Research Articles

Characterization of clostridial species and sulfite-reducing anaerobes isolated from foie gras with respect to microbial quality and safety

Anaerobic sulfite-reducing bacteria are generally considered as indicators of clostridial contamination in meat products. We reconsidered the relevance of this indicator for crude and pasteurized foie gras. A three-year study was conducted to recover anaerobic sulfite-reducing bacteria from foie gras manufactures. Under anaerobic culture at 37 °C, 98 isolates were obtained from crude or pasteurized foie gras, surfaces and pepper used in the recipe and further identified. Heat-treated products lead to the exclusive isolation of Clostridium strains, but other samples demonstrated a high diversity of non-spore forming bacterial species. The diversity in the Clostridium group was also high, with 14 different species represented from the 49 clostridial isolates, including Clostridium perfringens and psychrotolerant species. All the 12 C. perfringens isolates belonged to type A, but none carried the enterotoxin gene. In addition, none of them was able to grow in foie gras at 8 °C over a 130-days period. Other species were also tested for their ability to grow in these conditions: only three isolates, identified as Clostridium sordellii, Clostridium tertium and Clostridium algidicarnis/putrefaciens, grew at 8 °C, exhibiting 5 to 6 log of population increase in 70 days. Consequently, regarding the risk of product spoilage, we recommend anaerobes enumeration at 37 °C for pasteurized foie gras products, or after a thermal treatment aiming at spore selection, for crude foie gras.

Fat, bile and gut microbes

Western-style diets could be contributing to the rapid increase in inflammatory bowel disease. New research suggests that dietary fat can alter bile composition and so favour the growth of pro-inflammatory gut microbes. See Letter p.104 Milk fat is shown here to potentiate experimental colitis in susceptible mice, in association with increased luminal concentrations of sulphite-reducing bacteria. Mice fed a diet with comparable caloric intake containing unsaturated fatty acids are protected. The inflammation is caused by milk-fat-promoted taurine conjugation with bile acids, which increases the availability of organic sulphur used by the bacteria. This finding supports the suggestion that the recent upwards trend in complex immune disorders such as inflammatory bowel diseases could reflect changes in human microbiomes elicited in genetically susceptible individuals by dietary and other environmental changes.

Diversity and distribution of sulphate-reducing bacteria in human faeces from healthy subjects and patients with inflammatory bowel disease

The relative abundance of different groups of sulphate-reducing bacteria (SRB) in faecal DNA collected before and after therapy from patients suffering from Crohn's disease (CD), irritable bowel syndrome (IBS) or ulcerative colitis (UC) has been compared with that from healthy controls. Growth tests revealed that SRB were not more abundant in samples from patients with CD before treatment than in the healthy control group. For most of the 128 samples available, these preliminary results were confirmed using degenerate PCR primers that amplify the dsrAB gene. However, some samples from patients with CD before treatment contained a growth inhibitor that was absent from IBS or UC samples. In-depth sequencing of PCR-generated dsrB fragments revealed that the diversity detected was surprisingly low, with only eight strains of SRB and the sulphite-reducing bacterium, Bilophila wadsworthia, detected above the 0.1% threshold. The proportion of the two major species detected, B. wadsworthia and Desulfovibrio piger, was as high as 93.5% of the total SRB population in the healthy control group and lower in all patient groups. Four previously undescribed species were found: it is impossible to predict whether they are sulphate or sulphite-reducing bacteria.

The influence of vacuum packaging on microbiological status and sensory properties of fresh beef

The packaging method can significantly affect the shelf life of fresh meat, and consequently the microbiological status and sensory properties of the packaged meat. In our country, for extending the shelf life of meat and meat products, the vacuum-packaging and packaging in the modified atmosphere are usually used. Vacuum-packaging favours the growth of facultative anaerobic bacteria, including lactic acid bacteria, Enterobacteriaceae and Brochothrix thermosphacta, as proven spoilage bacteria of fresh meat. Vacuum packaging has a positive influence on juiciness, tenderness, flavor and ripening of meat, but it has negative influence on the meat color. The aim of the present study was to investigate the microbiological status and sensory properties of vacuum-packaged fresh beef. Samples of beef tenderlo in packaged in stretch foil and vacuum-packaged fresh beef tenderloin were kept in strictly controlled conditions, at 0-4°C. Microbiological and sensory examinations were performed on 1st, 7th, 14th, 21st and 28th day of storage, in three separate cycles. Microbiological examinations included determination of microbial indicators of the processing hygiene and microbial indicators of meat spoilage (total count of aerobic mesophilic and psychrophilic bacteria, the number of Enterobacteriaceae, the number of lactic acid bacteria, the number of Brochothrix thermosphacta) and determination of pathogens (Salmonella spp., coagulasepositive staphylococci, sulphite-reducing bacteria, E. coli, Listeria monocytogenes) as well. Sensory properties were evaluated by using quantitative-descriptive test, on a scale of 1 to 5. The following properties were evaluated: appearance of meat, the color of meat surface, the color of the meat intersection, structure, texture, smell of the fresh meat, smell of meat after cooking, taste of meat after cooking and roasting. By sensory analyses spoilage of meat was established on 21st day of investigation, in the first cycle and on 28th day, in the third cycle. Results obtained from microbiological examinations indicated meat spoilage on the same days, as well. In the second cycle of investigation the meat spoilage was established on 14th day of storage, although the microbiological results did not indicate the meat spoilage.

Effect of sanitary conditions and dietary fibre on the adaptation of gut microbiota after weaning

At weaning, the intestinal microbial ecosystem has to adapt to new feeds and to a new environment. The diverse and abundant commensal microbiota and its production of volatile fatty acids (VFA), especially butyrate, are involved in the prevention of diarrhoea and defence against pathogens. This study investigated the effects of the level of dietary fibre (DF) and sanitary housing conditions on the microbiota of weaned pigs. Forty-eight piglets, weaned at 28 days of age, were housed in clean or poor conditions. They were fed during two consecutive phases, two diets containing a high level (16.9 then 21.7% total dietary fibre-TDF, mainly soluble) or a low level DF (control, 12.1 then 14.6% TDF). Five weeks after weaning, microbiota was analysed using counting techniques and VFA profiles were determined by gas chromatography in faeces collected from the rectum. When compared with the clean conditions, the faeces of piglets housed in the poor environment contained significantly more Lactobacillus and Enterobacteria and less anaerobic sulphite-reducing bacteria (+ 0.9, + 1.1, −2.1 Log 10 CFU/g faeces), 60% more total VFA, with proportionally less acetate and more butyrate (−3%, + 4%). The introduction of DF did not affect the composition of the microbiota, tended to increase total VFA (25%), and decreased the level of branched-chain VFA (−1.4%). To conclude, the degraded sanitary housing conditions and to a lesser degree DF, stimulated the bacterial ecosystem in a way that could be beneficial for digestive balance, despite their negative impact on animal performances.

Microbial enumeration of different functional groups and bacterial behavior in acid basic conditions of a biotoxic landfill leachate of Bahía Blanca, Argentina.

Leachate is liquid waste from refuse biological decomposition or rainwater percolation in a landfill. This research focused on leachate produced by a landfill in Bahia Blanca, Buenos Aires, Argentina. The research studied the main microbial populations involved in wastewater treatment, analyzed the behavior of bacteria isolated from leachate at different pH values, and appraised leachate biotoxicity. The number of bacteria varied by type, ranging from 1 x 10(4) to 1 x 10(5) CUF/mL aerobic heterotrophic bacteria (AHB); 1 x 10(3) to 1 x 10(5) CUF/mL anaerobic heterotrophic bacteria (ANHB); 1 x 10(5) to 1 x 10(6) CUF/mL sulfite-reducing bacteria (SRB); 1 x 10(3) to 1 x 10(6) NMP/mL nitrate-reducing bacteria (NRB); and 1 x 10(2) to 1 x 10(4) NMP/mL ammonium-oxidizing bacteria (AOB). Several microbial strains developed at pH 5, 7, and 10. These pH values changed to 9 in the culture media after a 48-hour incubation. Leachate was used to water lettuce seeds (Lactuca sativa capitata). Its toxicity was proved by full inhibition of plant development.

The Crystal Structure of Desulfovibrio vulgaris Dissimilatory Sulfite Reductase Bound to DsrC Provides Novel Insights into the Mechanism of Sulfate Respiration

Sulfate reduction is one of the earliest types of energy metabolism used by ancestral organisms to sustain life. Despite extensive studies, many questions remain about the way respiratory sulfate reduction is associated with energy conservation. A crucial enzyme in this process is the dissimilatory sulfite reductase (dSiR), which contains a unique siroheme-[4Fe4S] coupled cofactor. Here, we report the structure of desulfoviridin from Desulfovibrio vulgaris, in which the dSiR DsrAB (sulfite reductase) subunits are bound to the DsrC protein. The alpha(2)beta(2)gamma(2) assembly contains two siroheme-[4Fe4S] cofactors bound by DsrB, two sirohydrochlorins and two [4Fe4S] centers bound by DsrA, and another four [4Fe4S] centers in the ferredoxin domains. A sulfite molecule, coordinating the siroheme, is found at the active site. The DsrC protein is bound in a cleft between DsrA and DsrB with its conserved C-terminal cysteine reaching the distal side of the siroheme. We propose a novel mechanism for the process of sulfite reduction involving DsrAB, DsrC, and the DsrMKJOP membrane complex (a membrane complex with putative disulfide/thiol reductase activity), in which two of the six electrons for reduction of sulfite derive from the membrane quinone pool. These results show that DsrC is involved in sulfite reduction, which changes the mechanism of sulfate respiration. This has important implications for models used to date ancient sulfur metabolism based on sulfur isotope fractionations.

Efficiency of a prebiotic and a plant extract alone or in combination on broiler performance and intestinal physiology

A 36-d trial was conducted to evaluate two potential alternatives to antibiotic growth promoters in broilers. The products tested were a prebiotic (PROFEED®) and a plant extract (XTRACT™). Ross male broiler performance and digestive tract function responses were studied. To evaluate the effect of these potential alternatives alone or in combination, seven diets were tested: positive control avilamycin 10 ppm (PC); negative control antibiotic-free (NC); NC + PROFEED® 600 ppm (P); NC + XTRACT™ 100 ppm (X); NC + PROFEED®/XTRACT™ 600/100 ppm (XPH); NC + PROFEED® /XTRACT™ 450/75 ppm (XPM); NC + PROFEED®/XTRACT™ 300/50 ppm (XPL). From 22 to 36 d of age, body weight gain (BWG) was improved by P, X, and XPM compared with NC (P < 0.05). Throughout the trial, broilers fed PC, P, X and XPL had a better feed conversion ratio (FCR) than those fed NC (P < 0.1). No relevant negative effect was observed for the parameters relative to the digestive tract function: ileal histomorphometry, anaerobic sulphite-reducing bacteria count (ASR), intestinal and caecal pH, caecal volatile fatty acids production (VFA) and litter score (LS). With the higher mixture dose (XPH), no improvement in broiler performance was observed, suggesting no synergistic effect of the two additives. Key words: Broiler, antibiotic growth promoter, plant extract, prebiotic

Distribution and persistence of fecal bacterial populations in liquid and dewatered sludge from a biological treatment plant

The changes in composition and structure of fecal coliforms (FC) and enterococci (ENT) populations, as well as the elimination of spores of sulphite-reducing bacteria (SRB), were compared between municipal sewage and their derived sludge in a biological treatment plant in order to determine any selective reduction or adsorption to sludge during the treatment process. Additionally, the persistence of antibiotic-resistant enterococcal populations in two kinds of sludge was also considered to evaluate their potential elimination in the treatment process. Microbial indicators, vancomycin-resistant and erythromycin-resistant enterococci were enumerated. The structure and composition of FC and ENT populations were determined by biochemical fingerprinting and clustering analyses. Raw and treated sewage showed a concentration of FC 1 log unit higher than ENT and nearly 2 log units higher than spores of SRB. However, the three studied indicators showed similar concentrations in both types of sludge. Consequently, FC were eliminated in higher proportion than ENT and spores of SRB in sludge. FC and ENT populations showed high diversity and similarity population indexes for all kinds of samples. Antibiotic-resistant enterococci persisted in a similar proportion in respect to total enterococci not only in treated sewage but also in sludge. The persistence of antibiotic-resistant strains in sludge as well as in treated sewage should be considered if they are used for land disposal or for water reutilization, respectively.

The composition and persistence of faecal coliforms and enterococcal populations in sewage treatment plants.

The changes in structure and composition of faecal coliforms and enterococcal populations in sewage from different treatment plants, and the elimination of vancomycin- and erythromycin-resistant enterococci (VRE and ERE, respectively) in these treatment plants was analysed to determine any selective reduction. Faecal coliforms, enterococci, VRE, ERE and spores of sulphite-reducing bacteria were enumerated using standard methods. Samples were enriched where necessary in order to isolate antibiotic resistant strains. The structure and composition of these bacterial populations were determined by biochemical fingerprinting and clustering analysis. High diversity and similarity indexes were detected among all the bacterial populations in raw and treated sewage, independently of their origin and the treatment processes employed. Antibiotic resistant strains were detected in all sewage tested and no selective reduction was observed. The faecal coliforms and enterococci populations did not differ in the sewage samples studied. The vancomycin and erythromycin resistances of the enterococcal populations were similar in the sewage samples. Resistance to both antibiotics persisted after the treatment process independently of raw sewage flow, faecal origin or size of the human population contributing to sewage. However, sewage of mixed origin (human and animal) presented a lower similarity index for the two bacterial populations compared with that of the other human sewage analysed. Although a significant reduction in bacterial populations was observed, the persistence of VRE and ERE strains in the same proportions in sewage suggests that there is no selective elimination of bacterial populations during the treatment processes. The ability of antibiotic resistance strains to survive sewage treatment systems should be considered in certain water reuse programmes.

A microbiota da carcaça e da carne ovina tratada com ácido acético, embalada a vácuo e maturada por 48 dias

Foi avaliada a carga de bacterias mesofilas e coliformes totais e fecais na superficie da carcaca ovina apos 12 horas do abate. Posteriormente, a carne foi cortada em fatias de aproximadamente 3cm de espessura, imersas por um minuto em acido acetico 1% ou em agua, embaladas individualmente a vacuo e armazenadas a 1°C. Nos dias 3,13, 23, 33 e 48 de maturacao as carnes foram analisadas para bacterias mesofilas e psicrotroficas, mofos e leveduras, coliformes totais e fecais, salmonela e clostridios sulfito-redutores. As contagens de bacterias mesofilas e psicrotroficas foram menores (p<0,05) nas carnes tratadas com acido acetico que nas nao tratadas nos dias 13 e 23 e nos dias 3 e 13 de maturacao, respectivamente. A contagem de mofos e leveduras foi menor (p<0,05), nas carnes tratadas em relacao as nao tratadas, apenas nos dias 13 e 23 de maturacao. Apos 3 dias de maturacao as carnes tratadas mostraram menores (p<0,05) contagens de coliformes fecais e totais que as nao tratadas. As carnes apresentaram presenca de salmonela com 3, 13 e 23 dias de maturacao mais nao com 33 e 48. Nao foi detectada presenca de clostridios sulfito-redutores durante todo o periodo de maturacao. Pode-se concluir que o tratamento com acido e as condicoes de maturacao utilizadas neste experimento mantem baixas contagens de microrganismos mesofilos, psicrotroficos, mofos e leveduras e coliformes por 13 dias. Durante este periodo, porem, inibicao do crescimento de salmonelas somente foi detectada apos 33 dias de maturacao da carne ovina.

Performance of a thermophilic sulfate and sulfite reducing high rate anaerobic reactor fed with methanol.

Thermophilic sulfate and sulfite reduction was studied in lab-scale Expanded Granular Sludge Bed (EGSB) reactors operated at 65 degrees C and pH 7.5 with methanol as the sole carbon and energy source for the sulfate- and sulfite-reducing bacteria. At a hydraulic retention time (HRT) of 10 h, maximum sulfite and sulfate elimination rates of 5.5 g SO3(2-) L(-1) day(-1) (100% elimination) and 5.7 g SO4(2-) L(-1) day(-1) (55% elimination) were achieved, resulting in an effluent sulfide concentration of approximately 1800 mg S L(-1). Sulfate elimination was limited by the sulfide concentration, as stripping of H2S from the reactor with nitrogen gas was found to increase the sulfate elimination rate to 9.9 g SO4(2-) L(-1) day(-1) (100% elimination). At a HRT of 3 h, maximum achievable sulfite and sulfate elimination rates were even 18 g SO3(2-) L(-1) day(-1) (100% elimination) and 11 g SO4(2-) L(-1) day(-1) (50% elimination). At a HRT of 3 h, the elimination rate was limited by the biomass retention of the system. 5.5 +/- 1.8% of the consumed methanol was converted to acetate, which was not further degraded by sulfate reducing bacteria present in the sludge. The acetotrophic activity of the sludge could not be stimulated by cultivating the sludge for 30 days under methanol-limiting conditions. Omitting cobalt as trace element from the influent resulted in a lower acetate production rate, but it also led to a lower sulfate reduction rate. Sulfate degradation in the reactor could be described by zeroth order kinetics down to a threshold concentration of 0.05 g L(-1), while methanol degradation followed Michaelis-Menten kinetics with a Km of 0.037 g COD L(-1).

Purification of a contaminated thermal well at an oil drilling site

The thermal water from the well MT-4 in Northeast Slovenia contains many organic micropollutants of geogenic origin because of the nearby oil fields. Therefore, a special technological treatment was necessary to make the water suitable for bathing: consisting of flocculation, sand filtration, and adsorption on granular activated carbon. We managed to remove not only all potentially toxic organic substances, but also the mesophilic bacteria (CFU) as well as sulfite reducing bacteria. On the other hand, all the important physical chemical parameters of water remained practically unchanged. In this way a hygienic water quality for balneological purposes was obtained. ©1999 John Wiley & Sons, Inc. Environ Toxicol 14: 211–216, 1999

Evolution of histidine decarboxylase bacterial groups during the ripening of Spanish semi-preserved anchovies.

We have studied the count evolutions of total aerobic mesophilic microorganisms, psychotrophic microorganisms, enterobacteria, faecal coliforms, sulphite-reducing bacteria and vibrio in spanish semi-preserved anchovies. These microorganisms are a sanitary index of the product and may produce high concentrations of histamine in both fresh and processed fish. The influence of NaCl concentration, redox potential, oxygen concentration and pH on bacterial growth have also been studied. With the exception of the sulphite-reducers and vibrio, the counts of the different bacterial groups decreased during the first two weeks of ripening, but later stabilized. The faecal coliforms did not appear in the culture media after these first two weeks, and the enterobacteria, what initially did not appear after first two weeks too, are detected at final phases probably for the final manipulation of elaboration processes. The count of the sulfite-reducers remained unchanged during the whole ripening process. Vibrio were not detected in any of the samples studied. NaCl and oxygen concentrations were the main factors influencing the decreasing bacterial counts. According to our results, the accumulation of high histamine concentrations in salted fish could be due to poor quality of the raw material, to inadequate handling or to other causes during its shelf life. The relationship with the histamine activity is probably due more to the presence of the halophilic or halotolerant microorganisms.

Initial investigation of microbially influenced corrosion (MIC) in a low temperature water distribution system

Abstract The purpose of this study was to determine if microorganisms could be considered a significant contributor to distribution system corrosion where year-round water temperatures remain near zero degrees Celsius. Initial evidence indicates that a heterogeneous population of potentially corrosive microorganisms were present in untreated supply water, treated water and corrosion tubercles. This included sulfite-reducing bacteria ( Clostridium species), sulfate-reducers; iron-reducing bacteria ( Bacillus species, Clostridium sp., Escherichia coli, Enterobacter aerogenes, Klebsiella oxytoca, Klebsiella pneumoniae, Pseudomonas aeruginosa, Pseudomonas cepecia, Pseudomonas fluorescens ), sulfur-oxidizing bacteria ( Thiobacillus thiooxidans, Thiobacillus thioparus ), iron-precipitating bacteria ( Leptothrix, Gallionella, Sphaerotilus ), sulfate-reducing actinomycetes and iron-reducing fungi ( Penicillium, Rhizopus, Aspergillus ). Corrosion tubercles contained greater numbers of coliforms than did the untreated supply or treated water. The ability of corrosion tubercles to sustain a diverse population of direct and opportunistic pathogens, able to participate in the corrosion process, may be an unrealized vector in the transmission of certain waterborne diseases to potential risk groups. In addition, corrosion tubercles may serve as a habitat for certain taste and odor-producing actinomycetes and fungi in treated water supplies. The ecology of these microorganisms, their influence on the corrosion process and the potential health impact needs to be investigated further.

Water supply and health, balancing between questions and answers

Publisher Summary This chapter discusses the complexity of the quality aspects of potable water supply. Water flowing through rivers, filters, mains, organs of organisms, and sewary systems collects a wide variety of contaminants, such as pathogenic bacteria, viruses, cysts, salts, metals, fibers, humic acids, pesticides, solvents, and oil components. Although all water quality aspects are relevant in each nation, a certain specialization in research areas can be distinguished, as specific problems are more urgent in one part of the world than in another. Pathogenic microorganisms continue to be a potential threat for the health of the tap water consumer. These organisms are ubiquitous in the raw water sources, and the safety of the drinking water therefore completely depends on the reliability of the water treatment system. As enterovirusses are more resistant to disinfection than the generally studied indicator bacteria, the search to find better indicator organisms—such as coliphages or spores of sulphite reducing bacteria—needs to be continued. It may be expected that in the future microbiological water examination will obtain again the dominating position it had in water quality monitoring in the past decades.

Bacteriological Quality of Ready-Mixed Mink Feed in Finland

Frozen samples of Finnish ready-mixed mink feed were analyzed for total bacterial count, the number of faecal streptococci, the coliform count, the number of haemolytic bacteria and the number of sulphite-reducing bacteria. The investigation comprised 242 feed samples from 38 central kitchens and larger private farm kitchens, the combined feed production of which is about 85 % of the yearly feed production of Finland. Of all samples 48.3 % had a total bacterial count of 106 … 6} × 106 bacteria per g of feed. The total bacterial count was relatively constant during the first four production periods of the year (December-August) and was elevated during the last period (September-November). The percentage of samples containing less than 2.5 × 104 faecal streptococci per g of feed was 49.8 %; 62 % of the samples contained less than 2.5 × 104 coliform bacteria per g. The content of coliform bacteria was lowest during the third production period (May); 48.5 % of the samples contained 5 × 103 … 105 haemolytic bacteria per g, and 4.6 % were negative. The content of haemolytic bacteria was relatively constant during the whole production year; 52.6 % of the feed samples contained 5 × 103 … 105 sulphite-reducing bacteria per g, and 17.2 % were negative. The mean content of sulphite-reducing bacteria was lowest during the second production period (March-April). The results are discussed and compared with corresponding results from Norway and Denmark.

The discovery of nature's biosynthetic pathways.

Uro'gen-III is a key intermediate on the biosynthetic pathways to the vitally important natural pigments haem, chlorophyll and the cytochromes. How the unexpected structure of uro'gen-III is synthesized by living things has long been a major puzzle. Studies based on 13C-labelling are described which show a) that a single intramolecular rearrangement occurs and b) that this step occurs after the open-chain linear tetrapyrrole system has been built. A second study involves stereospecific labelling with deuterium and tritium to elucidate the absolute stereochemistry of the enzymic reaction sequence which produces the vinyl groups of haem. The third and last section of the lecture is focussed on the biosynthetic intermediates lying between uro'gen-III and cobyrinic acid on the pathway to vitamin B12. An octacarboxylic isobacteriochlorin is isolated from a vitamin B12-producing organism and this is shown to be identical with sirohydrochlorin, previously obtained by Kamin and Siegel as the metal-free prosthetic group of certain sulphite-reducing bacteria. The structure and absolute stereochemistry of sirohydrochlorin are studied and comment is made on the evolutionary interest of these findings.

The Correlation of Sulphite Reducing and Colon Bacteria in Water

The bacterial reduction of sulphites in media containing a fermentable carbohydrate and metallic salts was first studied by Wilson (1921). In subsequent investigations Wilson and Blair employed a sulphite-glucose-iron agar for the quantitative estimation of the number of B. welchii and other reducing bacteria in water. In the first of these investigations (1924), 54 samples, including 21 shallow wells, 9 springs, 15 catchment reservoirs, 8 sand filters and one river were analyzed. It was found that sulphite reducing bacteria were absent from non-polluted supplies and the conclusion was reached that water in shallow wells and springs containing more than two reducing colonies per 10 cc. should be regarded with suspicion. In a more extended investigation (1925), these workers examined 252 samples of water from various sources to determine the correlation of the sulphite reduction test and tests for colon bacteria. The number of dark sulphide colonies varied from none in waters of high sanitary quality to several hundred in polluted supplies. Waters from clean mountain valleys, reservoirs and clean catchment areas never contained more than 1 or 2 per 40 cc. The results show some degree of correlation between the test for B. coli and the reduction test. The number of sulphite reducing colonies usually varied from 5 to 320 per 40 cc. when the B. coli presumptive test was positive in 0.1 cc. Frequently, however, sulphite reducing organisms were not found even when the presumptive test was positive with 0.1 or 1.0 cc. In twenty such instances the coliform bacteria were found to belong to the aerogenes group. The conclusion was reached that a definite correlation exists between colon bacteria of fecal origin and sulphite reducing bacteria in water, and that the sulphite reduction test is a valuable supple-