Uneven distribution of aerobic mesophilic bacteria on human skin.

Viable aerobic mesophilic bacteria are not evenly distributed on the skin of the volar forearm. An increase in the size of the area sampled did not result in a proportional increase in the number of the viable aerobic mesophilic bacteria recovered.     

Microbiology of Ensiled High-Moisture Corn

The effects of gaseous environment and temperature on the microbial populations of ensiled high-moisture corn were investigated. Molds, coliform bacteria, mesophilic aerobic bacteria, and yeasts were enumerated at intervals during ensiling. The numbers of aerobic bacteria were similar in structures containing different concentrations of gas and held at different temperatures. Coliform bacteria could not be detected after 10 days of ensiling. Mold numbers were relatively low, but were important in the deterioration of corn at the surface of the silos. Yeast and bacterial numbers increased rapidly following an initial aeration period, but no increase was observed after a second aeration series. Lack of a growth response to the second aeration series is believed related to the depletion of an assimilable carbon source.     

The phylogenetic diversity of aerobic organotrophic bacteria from the Dagan high-temperature oil field

The distribution and species diversity of aerobic organotrophic bacteria in the Dagan high-temperature oil field (China), which is exploited via flooding, have been studied. Twenty-two strains of the most characteristic thermophilic and mesophilic aerobic organotrophic bacteria have been isolated from the oil stratum. It has been found that, in a laboratory, the mesophilic and thermophilic isolates grow in the temperature, pH, and salinity ranges characteristic of the injection well near-bottom zones or of the oil stratum, respectively, and assimilate a wide range of hydrocarbons, fatty acids, lower alcohols, and crude oil, thus exhibiting adaptation to the environment. Using comparative phylogenetic 16S rRNA analysis, the taxonomic affiliation of the isolates has been established. The aerobic microbial community includes gram-positive bacteria with a high and low G+C content of DNA, and gamma and beta subclasses of Proteobacteria. The thermophilic bacteria belong to the genera Geobacillus and Thermoactinomyces, and the mesophilic strains belong to the genera Bacillus, Micrococcus, Cellulomonas, Pseudomonas, and Acinetobacter. The microbial community of the oil stratum is dominated by known species of the genus Geobacillus (G. subterraneus, G. stearothermophilus, and G. thermoglucosidasius) and a novel species "Geobacillus jurassicus." A number of novel thermophilic oil-oxidizing bacilli have been isolated.     

Description of heterotrophic bacteria occurring in paper mills and paper products

AIMS: To isolate aerobic mesophilic bacilli and thermophilic bacteria from different paper mill samples and to evaluate their potential harmfulness. METHODS AND RESULTS: A total of 109 mesophilic and 68 thermophilic isolates were purified and characterized by automated ribotyping and partial 16S rDNA sequencing. The mesophilic isolates belonged to the genera Bacillus (13 taxa), Brevibacillus (three taxa) and Paenibacillus (five taxa). The thermophilic bacteria represented seven taxa of Bacillus, Geobacillus or Paenibacillus, four of proteobacteria and one of actinobacteria. The most frequently occurring bacteria were Bacillus cereus, B. licheniformis, Pseudoxanthomonas taiwanensis and bacteria closely related to Paenibacillus stellifer, P. turicensis or Leptothrix sp. One mill was contaminated throughout with bacteria of a novel mesophilic genus most closely related to Brevibacillus centrosporus and another with bacteria of a novel thermophilic genus most closely related to Hydrogenophilus thermoluteolus. One B. cereus isolate producing haemolytic diarrhoeal enterotoxin was detected and all the tested B. licheniformis isolates produced a metabolite toxic to boar sperm cells. CONCLUSIONS: The bacilli and thermophilic bacteria isolated represent species which should not present occupational hazards in paper mill environments. The most harmful bacterium detected was B. licheniformis and potentially also B. cereus. SIGNIFICANCE AND IMPACT OF THE STUDY: Knowledge of the microbial diversity in a paper mill provides a rational basis for development of an effective controlling programme. A database constructed from the fingerprints generated using automated ribotyping helps to identify and trace the contamination routes of bacteria occurring in paper mills.     

Chemical and sensory quality changes in fish balls prepared from Alburnus mossulensis Heckel, 1843 during frozen storage

The effects of frozen storage on fish balls derived from Alburnus mossulensis at −18 ± 2°C were studied. Several chemical parameters were determined [pH, total volatile basic nitrogen (TVB‐N), thiobarbituric acid (TBA), free fatty acids (FFA)]. Further, microbiological effects were analysed during storage [Total mesophilic aerobic bacteria (TMAB), total psychrophilic bacteria (TPB), coliform and yeast‐mould count]. Finally, sensory quality tests were performed with fresh and stored balls. Fish balls were composed of 64% fish meat and 36% other ingredients, including: 18% boiled rice, 11.4% onions, 1.8% parsley, 3.8% fat, 0.7% salt and 0.26% black pepper. This basic mixture was processed to form small (25 g) balls and a pre‐cooking process was applied. Test balls were divided into two groups: vacuum packed (A1) and a control group without vacuum (A2). Test packages were stored for 6 months, resulting in increased pH, TVB‐N, TBA and FFA, while the values for sensory properties declined. However, these changes did not drop below the limit of acceptance. Total mesophilic aerobic bacteria and total psychrophilic bacteria were significantly reduced in both A1 and A2 groups.     

The Phylogenetic Diversity of Aerobic Organotrophic Bacteria from the Dagang High-Temperature Oil Field

The distribution and species diversity of aerobic organotrophic bacteria in the Dagang high-temperature oil field (China), which is exploited with water-flooding, have been studied. Twenty-two strains of the most characteristic thermophilic and mesophilic aerobic organotrophic bacteria have been isolated from the oil stratum. It has been found that, in a laboratory, the mesophilic and thermophilic isolates grow in the temperature, pH, and salinity ranges characteristic of the injection well near-bottom zones or of the oil stratum, respectively, and assimilate a wide range of hydrocarbons, fatty acids, lower alcohols, and crude oil, thus exhibiting adaptation to the environment. Using comparative phylogenetic 16S rRNA analysis, the taxonomic affiliation of the isolates has been established. The aerobic microbial community includes gram-positive bacteria with a high and low G+C content of DNA, and γ and β subclasses of Proteobacteria. The thermophilic bacteria belong to the genera Geobacillus and Thermoactinomyces, and the mesophilic strains belong to the genera Bacillus, Micrococcus, Cellulomonas, Pseudomonas, and Acinetobacter. The microbial community of the oil stratum is dominated by known species of the genus Geobacillus (G. subterraneus, G. stearothermophilus, and G. thermoglucosidasius) and a novel species “Geobacillus jurassicus.” A number of novel thermophilic oil-oxidizing bacilli have been isolated.__________Translated from Mikrobiologiya, Vol. 74, No. 3, 2005, pp. 401–409.Original Russian Text Copyright © 2005 by Nazina, Sokolova, Shestakova, Grigoryan, Mikhailova, Babich, Lysenko, Tourova, Poltaraus, Qingxian Feng, Fangtian Ni, Belyaev.     

Time series analysis of aerobic bacterial flora during Miso fermentation

AIMS: This article reports a microbiological study of aerobic mesophilic bacteria that are present during the fermentation process of Miso. METHODS AND RESULTS: Aerobic bacteria were enumerated and isolated from Miso during fermentation and divided into nine groups using traditional phenotypic tests. The strains were identified by biochemical analysis and 16S rRNA sequence analysis. They were identified as Bacillus subtilis, B. amyloliquefaciens, Kocuria kristinae, Staphylococcus gallinarum and S. kloosii. All strains were sensitive to the bacteriocins produced by the lactic acid bacteria isolated from Miso. CONCLUSIONS: The dominant species among the undesirable species throughout the fermentation process were B. subtilis and B. amyloliquefaciens. It is suggested that bacteriocin-producing lactic acid bacteria are effective in the growth prevention of aerobic bacteria in Miso. SIGNIFICANCE AND IMPACT OF THE STUDY: This study has provided useful information for controlling of bacterial flora during Miso fermentation.     

Monitoring Dental-Unit-Water-Line Output Water by Current In-office Test Kits

The importance of monitoring contamination levels in the output water of dental-unit-water-lines (DUWLs) is essential as they are prone to developing biofilms that may contaminate water that is used to treat patients, with opportunistic pathogens such as species of Legionella, Pseudomonas and others. Dentists and practice staff are also at risk of being infected by means of cross-infection due to aerosols generated from DUWL water. The unit of measurement for the microbial contamination of water by aerobic mesophilic heterotrophic bacteria is the colony-forming unit per millilitre (cfu/ml) of water. The UK has its own guidelines set by the Department of Health for water discharged from DUWL to be between 100 and 200 cfu/ml of water. The benchmark or accepted standard laboratory test is by microbiological culture on R2A agar plates. However, this is costly and not convenient for routine testing in dental practices. A number of commercial indicator tests are used in dental surgeries, but they were not developed for the dental market and serve only to indicate gross levels of contamination when used outside of the manufacturer’s recommended incubation period. The aim of this article is to briefly review the universal problem of DUWL contamination with microbial biofilms and to update dental professionals on the availability of currently available commercial in-office monitoring systems for aerobic mesophilic heterotrophic bacteria and to discuss their limitations for testing water samples in assuring compliance with recommended guidelines.     

Anoxygenic phototrophic bacteria from microbial communities of Goryachinsk thermal spring (Baikal Area,Russia)

Species composition of anoxygenic phototrophic bacteria in microbial mats of the Goryachinsk thermal spring was investigated along the temperature gradient. The spring belonging to nitrogenous alkaline hydrotherms is located at the shore of Lake Baikal 188 km north-east from Ulan-Ude. The water is of the sulfate-sodium type, contains trace amounts of sulfide, and salinity does not exceed 0.64 g/L, pH 9.5. The temperature at the outlet of the spring may reach 54°C. The cultures of filamentous anoxygenic phototrophic bacteria, nonsulfur and sulfur purple bacteria, and aerobic anoxygenic phototrophic bacteria were identified using the pufLM molecular marker. The fmoA marker was used for identification of green sulfur bacteria. Filamentous cyanobacteria predominated in the mats, with anoxygenic phototrophs comprising a minor component of the phototrophic communities. Thermophilic bacteria Chloroflexus aurantiacus were detected in the samples from both the thermophilic and mesophilic mats. Cultures of nonsulfur purple bacteria similar to Blastochloris sulfoviridis and Rhodomicrobium vannielii were isolated from the mats developed at high (50.6–49.4°C) and low temperatures (45–20°C). Purple sulfur bacteria Allochromatium sp. and Thiocapsa sp., as well as green sulfur bacteria Chlorobium sp., were revealed in low-temperature mats. Truly thermophilic purple and green sulfur bacteria were not found in the spring. Anoxygenic phototrophic bacteria found in the spring were typical of the sulfur communities, for which the sulfur cycle is mandatory. The presence of aerobic bacteriochlorophyll a-containing bacteria identified as Agrobacterium (Rhizobium) tumifaciens in the mesophilic (20°C) mat is of interest.     

Diversity surveys and evolutionary relationships of aoxB genes in aerobic arsenite-oxidizing bacteria

A new primer set was designed to specifically amplify ca. 1,100 bp of aoxB genes encoding the As(III) oxidase catalytic subunit from taxonomically diverse aerobic As(III)-oxidizing bacteria. Comparative analysis of AoxB protein sequences showed variable conservation levels and highlighted the conservation of essential amino acids and structural motifs. AoxB phylogeny of pure strains showed well-discriminated taxonomic groups and was similar to 16S rRNA phylogeny. Alphaproteobacteria-, Betaproteobacteria-, and Gammaproteobacteria-related sequences were retrieved from environmental surveys, demonstrating their prevalence in mesophilic As-contaminated soils. Our study underlines the usefulness of the aoxB gene as a functional marker of aerobic As(III) oxidizers.     

Microbial degradation of the organophosphate pesticide, Ethion

The organophosphate pesticide, Ethion, remains a major environmental contaminant in rural Australia and poses a significant threat to environmental and public health. The aerobic degradation of Ethion by mesophilic bacteria isolated from contaminated soils surrounding disused cattle dip sites was investigated. Two isolates, identified as Pseudomonas and Azospirillum species, were capable of biodegrading Ethion when cultivated in minimal salts medium. The abiotic hydrolytic degradation products of Ethion such as Ethion Dioxon and O,O-diethylthiosphosphate were not detected. The data suggest the rapid degradation of Ethion to support microbial growth. The results have implications for the development of a bioremediation strategy.     

Evolutionary timing of the origins of mesophilic sulphate reduction and oxygenic photosynthesis: a phylogenomic dating approach

Until recently, the deep‐branching relationships in the bacterial domain have been unresolved. A new phylogenetic approach (termed compartmentalization) was able to resolve these deep‐branching relationships successfully by using a large number of genes from whole genome sequences and by reducing long branch attraction artefacts. This new, well‐resolved phylogenetic tree reveals the evolutionary relationships between diverse bacterial groups that leave important traces in the geological record. It shows that mesophilic sulphate reducers originated before the Cyanobacteria, followed by the origination of sulphur‐ and pyrite‐oxidizing bacteria after oxygen became available in the biosphere. This evolutionary pattern mirrors a similar pattern in the Palaeoproterozoic geological record. Sulphur isotopic fractionation records indicate that large‐scale bacterial sulphate reduction began in marine environments around 2.45 billion years ago (Ga), followed by rapid oxygenation of the atmosphere about 2.3 or 2.2 Ga. Oxygenation was then followed by increasing oceanic sulphate concentrations (probably owing to pyrite oxidation and continental weathering), which then resulted in the disappearance of banded iron formations by 1.8 Ga. The similarity between the phylogenetic and geological records suggests that the geochemical changes observed on the Palaeoproterozoic Earth were caused by major origination events in the mesophilic bacteria, and that these geochemical changes then caused additional origination events, such as aerobic respiration. If so, then constraints on divergence dates can be established for many microbial groups, including the Cyanobacteria, mesophilic bacteria, mesophilic sulphate reducers, methanotrophs, several anoxygenic phototrophs, as well as for mitochondrial endosymbiosis. These dates may also help to explain a large number of other changes in the geological record of the Neoarchean and Palaeoproterozoic Earth. This hypothesis, however, does not agree with the finding of cyanobacterial and eukaryote lipids at 2.7 Ga, and suggests that further work needs to be done to elucidate the discrepancies in both these areas.     

Survival of Campylobacter jejuni in chicken meat at frozen storage temperatures

The aim of this study was to determine the survival of Campylobacter jejuni in chicken meat samples at frozen temperatures and given length of incubation and to determine the impact of aerobic bacteria on the survival of C. jejuni. The chicken meat samples were inoculated with C. jejuni NCTC 11351 suspensions and stored in bags at temperatures of -20°C and -70°C. The mean value of C. jejuni from meat samples decreased from 7.52 log10 CFU/g after 30 minutes of incubation at ambient temperature, to 3.87 log10 CFU/g on the eighth week of incubation at -20°C, and to 3.78 log10 CFU/g at incubation at -70°C after the same incubation period. Both freezing temperatures, -20°C and -70°C, decreased the number of campylobacters. The presence of aerobic mesophilic bacteria did not influence the survival of C. jejuni in chicken meet samples. Keeping poultry meat at freezing temperatures is important for the reduction of C. jejuni, which has a strong influence on the prevention of occurrence of campylobacteriosis in humans.     

Evaluation of analytical methods for determining the distribution of biofilm and active bacteria in a commercial heating system

Danish district heating systems have good water quality, but continue to suffer from biofouling and biocorrosion. Localisation analyses of bacteria using microautoradiography were performed for one system in order to obtain detailed information for solving these problems. A mass balance showed that 77% of the bacteria were located at surfaces, with 23% in the bulk water, and 9% of the total carbon originated from biomass, while 91% was dissolved in the bulk water. The presence of active bacteria was determined with microautoradiography which showed that biofilms contained 99% and 1% were in the bulk water. A high bacterial functional diversity was observed, with active mesophilic and thermophilic bacteria under aerobic and anaerobic conditions and with potentially corrosive biofilm bacteria present. The study reveals that by applying the activity based approach, the ratio of living and dead bacteria in the biofilm and bulk water in this type of system could be accurately determined. Also, the results emphasise that to minimise biofilm growth and biocorrosion, monitoring should be established focusing on the surfaces, since bulk water parameters do not reflect bacterial activity.     

Isolation and Identification of Psychrophilic Species of Bacillus from Milk

Forty isolates from 97 raw milk samples (heated to 80 C for 10 min and stored at 4 to 7 C for 3 to 4 weeks) were sporeforming, aerobic, gram-positive or gram-variable, rod-shaped bacteria. Fifteen isolates that were identified had characteristics similar to species of Bacillus, except that they had lower growth temperature ranges, were gram-variable, and were somewhat different in sugar fermentations. Four isolates grew well within 2 weeks at 0 C, but they grew faster at 20 to 25 C. These psychrophilic sporeforming bacteria, the importance of which is discussed, are considered to be variant strains of mesophilic bacilli adapted to low temperatures.     

Specialized cell surface structures in cellulolytic bacteria.

The cell surface topology of various gram-negative and -positive, anaerobic and aerobic, mesophilic and thermophilic, cellulolytic and noncellulolytic bacteria was investigated by scanning electron microscopic visualization using cationized ferritin. Characteristic protuberant structures were observed on cells of all cellulolytic strains. These structures appeared to be directly related to the previously described exocellular cellulase-containing polycellulosomes of Clostridium thermocellum YS (E. A. Bayer and R. Lamed, J. Bacteriol. 167:828-836, 1986). Immunochemical evidence and lectin-binding studies suggested a further correlation on the molecular level among cellulolytic bacteria. The results indicate that such cell surface cellulase-containing structures may be of general consequence to the bacterial interaction with and degradation of cellulose.     

Isolation and identification of threeCellulomonas spp. from forest soils

Three stains of cellulose-degrading, aerobic, mesophilic bacteria were isolated from forest soils and, from their cultural, biochemical, and physiological characteristics, they were identified as members of the genusCellulomonas. Unusual biochemical characteristics, e.g. urea hydrolysis, were observed in two isolates. These characteristics have not previously been reported for cellulomonads and may prove to be significant for characterization ofCellulomonas spp. The isolates were able to use urea as a N source in cellulose fermentation. All three strains were motile, with one to four peritrichous flagella observed. Amino acid and polysaccharide composition of the cell walls of the three isolates were identical.     

Microbiological evaluation of pequi (<Emphasis Type="Italic">Caryocar brasiliense</Emphasis> Camb.) preserves made from a typical Brazilian fruit

The microbiological quality of preserves made from the pulp of the pequi (Caryocar brasiliense Camb.), a typical Brazilian fruit, was assessed. The total aerobic mesophilic and the yeast and mould counts in the samples suggest inadequate hygienic conditions during the processing of the product. Low levels of contamination by coliform bacteria and enterobacteria were observed; however, the presence of injured cells of these microorganisms was demonstrated. The presence of Staphylococcus aureus and sulfite-reducing clostridia was not shown. Salmonella spp. was found in 33% of the samples analysed, indicating that the product can represent a public health risk.     

The new bacteriochlorophyll a-containing bacterium Roseinatronobacter monicus sp. nov. from the hypersaline soda Mono Lake (California, United States)

Two strains of pink-colored aerobic bacteriochlorophyll a-containing bacteria were isolated from aerobic (strain ROS 10) and anaerobic (strain ROS 35) zones of the water column of Mono Lake (California, United States). Cells of the bacteria were nonmotile oval gram-negative rods multiplying by binary fission by means of a constriction. No intracellular membranes were detected. Polyphosphates and poly-1-hydroxybutyric acid were the storage compounds. Pigments were represented by bacteriochlorophyll a and carotenoids of the spheroidene series. The strains were obligately aerobic, mesophilic (temperature optimum of 25-30 degrees C), alkaliphilic (pH optimum of 8.5-9.5), and halophilic (optimal NaCl concentration of 40-60 g/l). They were obligately heterotrophic and grew aerobically in the dark and in the light. Respiration was inhibited by light at wavelengths corresponding to the absorption of the cellular pigments. The substrate utilization spectra were strain-specific. In the course of organotrophic growth, the bacteria could oxidize thiosulfate to sulfate; sulfide and polysulfide could also be oxidized. The DNA G+C content was 59.4 mol % in strain ROS 10 and 59 mol % in strain ROS 35. In their phenotypic properties, the new strains were close but not identical to the alkaliphilic bacterium Roseinatronobacter thiooxidans. The distinctions in the nucleotide sequences of the 16S rRNA genes (2%) and low DNA-DNA hybridization level with Rna. thiooxidans (22-25%) allow the new strains to be assigned to a new species of the genus Roseinatronobacter, Roseinatronobacter monicus sp. nov.     

Microbial community dynamics in anaerobic bioreactors and algal tanks treating piggery wastewater

Integrated biosystem is becoming a major aspect of wastewater management practice. Microbial communities in piggery wastewater sampled from anaerobic (thermophilic and mesophilic) and aerobic digesters (algal tanks) during waste remediation were analyzed by culture-independent techniques based on polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). The use of Muyzer's 314F-GC, 518R bacterial primers, and archaeal A934F, 1309R primers followed by partial 16s rDNA sequence analysis of the main bands from DGGE revealed the presence of unknown and as yet uncultured microorganisms but also showed functional and ecologically significant denitrifying, acetogenic bacteria along with autotrophic, hydrogenotrophic, and acetoclastic methanogen archaea. Thermophilic digesters were dominated by γ-Proteobacteria, Methanothermobacter sp., while mesophilic digesters showed dominance by Firmicutes, uncultured bacteria, Methanosarcina, and Methanoculleus genera. Under aerobic conditions within algal tanks, pH rose from 7.17 to 9.32, with a significant decrease in total ammonia nitrogen, chemical oxygen demand, and soluble phosphorus levels. PCR-DGGE proved a useful tool for investigating the dynamics of microbial community in the bio-processing of piggery wastewater. Knowledge of the microbial communities involved in digestion of piggery wastewater will allow optimization of integrated biosystem by removing the main pollutants like inorganic ammonium-nitrogen, phosphorus, and pathogens from intensive farming system.