Degradation of Methylmercury by Bacteria Isolated from Environmental Samples

A total of 207 bacterial cultures, isolated from environmental samples, was screened for ability to degrade methylmercury. Of these, 30 were found positive for aerobic demethylation. Twenty-two of these were shown to be facultative anaerobes and 21 of these degraded methylmercury anaerobically. All positive species volatilized methylmercury aerobically, and methane was produced as a degradation product. Although methylmercury degradation was complete in most cases, material balances indicated some of the inorganic mercury formed was not volatilized and is presumed bound to the cells. All positive isolates were tolerant to at least 0.5 mug of methylmercury per ml, and the extent of volatilization of mercury increased with concentration to the threshold value. The results indicate that demethylating species are prevalent in the environment and may be important in suppressing the methylmercury content of sediments.     

Characterization of Hydrogen Sulfide-Producing Bacteria Isolated from Meat and Poultry Plants

A survey of the types of aerobic organisms able to produce H2S on peptone iron agar (Levin, 1968), and commonly occurring in meat and poultry plants, revealed that these could be divided into four distinct groups. The ability of representative strains of each type to grow at low temperatures and cause off-odors on chicken muscle was examined. The results are discussed in relation to the role of these organisms in the psychrophilic spoilage of meat and meat products.     

Characterization of Multi-Potential Toluene Metabolizing Bacteria Isolated from Tannery Effluents

Microbiology - The focus of present study was to isolate and characterize toluene metabolizing bacteria and evaluate their bioremediation potential. During present study bacteria were isolated from...     

Characterization of Acetanilide Herbicides Degrading Bacteria Isolated from Tea Garden Soil

Three different green manures were added to the tea garden soils separately and incubated for 40 days. After, incubation, acetanilide herbicides alachlor and metolachlor were spiked into the soils, separately, followed by the isolation of bacteria in each soil at designed intervals. Several bacterial strains were isolated from the soils and identified as Bacillus silvestris, B. niacini, B. pseudomycoides, B. cereus, B. thuringiensis, B. simplex, B. megaterium, and two other Bacillus sp. (Met1 and Met2). Three unique strains with different morphologies were chosen for further investigation. They were B. megaterium, B. niacini, and B. silvestris. The isolated herbicide-degrading bacteria showed optimal performance among three incubation temperatures of 30°C and the best activity in the 10 to 50 μg/ml concentration of the herbicide. Each bacterial strain was able to degrade more than one kind of test herbicides. After incubation for 119 days, B. cereus showed the highest activity to degrade alachlor and propachlor, and B. thuringiensis to degrade metolachlor.     

Characterization,Identification and Application of Lactic Acid Bacteria Isolated from Forage Paddy Rice Silage

There has been growing interest to develop forage rice as a new feed resource for livestock. This study was to characterize the natural population of lactic acid bacteria (LAB) and select potentially excellent strains for paddy rice silage preparation in China. One hundred and twenty-six strains were isolated and screened from paddy rice silage prepared using a small-scale fermentation system, and ninety-nine of these isolates were considered to be LAB based on their Gram-positive and catalase-negative morphology and the production of most of their metabolic products as lactic acid. These isolates were divided into eight groups (A-H) on the basis of their morphological and biochemical characteristics. The Group A to H strains were identified as Lactobacillus (L.) plantarum subsp. plantarum (species ratio: 8.1%), L. casei (5.1%), Leuconostoc (Ln.) pseudomesenteroides (11.1%), Pediococcus (P.) pentosaceus (24.2%), Enterococcus (E.) mundtii (12.1%), Lactococcus (Lc.) garvieae (15.2%), E. faecium (9.1%) and Lc. lactis subsp. lactis (15.2%) based on sequence analyses of their 16S rRNA and recA genes. P. pentosaceus was the most abundant member of the LAB population in the paddy rice silage. A selected strain, namely L. casei R 465, was found to be able to grow under low pH conditions and to improve the silage quality with low pH and a relatively high content of lactic acid. This study demonstrated that forage paddy rice silage contains abundant LAB species and its silage can be well preserved by inoculation with LAB, and that strain R 465 can be a potentially excellent inoculant for paddy rice silage.     

甘草内生细菌多样性研究

以分离培养的方法对内蒙古鄂尔多斯市甘草基地野生及栽培甘草内生细菌的多样性进行了初步研究。结果表明, 野生及栽培甘草植株内存在大量种群丰富的内生细菌。经ERIC-PCR指纹图谱分析, 共分离到120株内生细菌, 野生及栽培甘草均表现出根和叶部位的内生细菌数量多于茎部。对其中82株进行16S rDNA片段测序分析, 结果表明这些内生细菌分别与GenBank中α、β、γ-Proteobacteria、Firmicutes、Actinobacteria五类细菌中的19个已知属相似性达到97％～100%。内生细菌的主要优势种群为芽孢杆菌属(Bacillus sp.)、假单胞菌属(Pseudomonas sp.)、泛菌属( Pantoea sp.)和沙雷氏菌属(Serratia sp.)。     

Properties of Bacteria Isolated from Deep-Sea Sediments

Thirty-eight isolates were subjected to taxonomic analysis by computer. Of the 38 isolates, 31 were from sediment samples collected at depths from 9,400 to 10,400 meters in the Philippine and Marianas Trenches of the Pacific Ocean, and 7 cultures were from seawater samples collected at various depths from surface to 4,000 meters and from several locations in the Pacific Ocean. A total of 116 characteristics were determined for each isolate, coded, and transferred to punch cards. Similarity values were obtained by computer analysis, with the use of two recently developed computer programs. Five distinct phenetic clusters were observed from the numerical analyses. Four of the clusters were identified as species of the genus Pseudomonas, and one, as an aerogenic species of Aeromonas. Group IV was identified as pigmented Pseudomonas fluorescens, and the major cluster, consisting of groups I and II, which merged at a species level of similarity, was treated as a new species of Pseudomonas. The 38 strain data were compared with data for 132 marine and nonmarine strains previously subjected to computer taxonomic analysis. The barotolerant deep-sea strains, with the exception of the deep-sea P. fluorescens isolates, clustered separately from all other marine strains.     

甘草内生细菌多样性研究

以分离培养的方法对内蒙古鄂尔多斯市甘草基地野生及栽培甘草内生细菌的多样性进行了初步研究.结果表明,野生及栽培甘草植株内存在大量种群丰富的内生细菌.经ERIC-PCR指纹图谱分析,共分离到120株内生细菌,野生及栽培甘草均表现出根和叶部位的内生细菌数量多于茎部.对其中82株进行16S rDNA片段测序分析,结果表明这些内生细菌分别与GenBank中α、β、γ-Proteobacteria、Firmicutes、Actinobacteria五类细菌中的19个已知属相似性达到97%～100%.内生细菌的主要优势种群为芽孢杆菌属(Bacillus sp.)、假单胞菌属(Pseudomonas sp.)、泛菌属(Pantoea sp.)和沙雷氏菌属(Serratia sp.).     

Genomic Characterization of Human and Environmental Polioviruses Isolated in Albania

Between April and December 1996, a serious outbreak of poliomyelitis occurred in Albania; almost 140 subjects were involved, and the episode presented an unusually high mortality rate (12%). During the outbreak, water samples from the Lana River in Tirana, Albania, and stool samples from two cases of paralytic poliomyelitis were collected and analyzed for the presence of polioviruses. Six polioviruses were isolated from the environmental and human samples, according to standard methods. All the samples were characterized by partial genomic sequencing of 330 bases across the 5′ untranslated region (5′-UTR) (nucleotide positions 200 to 530) and of 300 bases across the VP1 region (nucleotide positions 2474 to 2774). Comparison of these sequences with those present in data banks permitted the identification of environmental isolates Lana A and Lana B as, respectively, a Sabin-like type 2 poliovirus and an intertypic recombinant poliovirus (Sabin-like type 2/wild type 1), both bearing a G instead of an A at nucleotide position 481. The two other environmental polioviruses were similar to the isolates from the paralytic cases. They were characterized by a peculiar 5′-UTR and by a VP1 region showing 98% homology with the Albanian epidemic type 1 isolates reported by other authors. This study confirms the environmental circulation in Albania of recombinant poliovirus strains, likely sustained by a massive vaccination effort and by the presence in the environment of a type 1 poliovirus, as isolated from the Lana River in Tirana about 2 months before the first case of symptomatic acute flaccid paralysis was reported in this town.     

Characterization of Cr(VI)-Resistant Bacteria Isolated from Chromium-Contaminated Soil by Tannery Activity

Bacterial strains, previously isolated from a chromium-polluted soil, were identified on the basis of Gram reaction and biochemical characteristics (Biolog system). Moreover, chromate MICs, chromate reduction capability, multiple heavy metal tolerance, and antibiotic susceptibility were tested for each isolate. All strains but one were Gram-positive and resistant to high concentrations of chromate. The most Cr(VI)-resistant isolate (22mM) was identified as Corynebacterium hoagii. All Cr(VI)-resistant strains except the isolate ChrC20 were capable of catalyzing the reduction of Cr(VI) to Cr(III), a less toxic and less water-soluble form of chromium. The only isolate Cr(VI)-sensitive, attributed to the Pseudomonas genus, also exhibited Cr(VI)-reduction. Isolates were also screened for the presence of plasmid DNA. The strains ChrC20 and ChrB20 harbored one and two plasmids of high molecular mass, respectively. This approach permitted selection of some bacterial strains, which could be used for bioremediation of Cr(VI)-polluted environments. Received: 21 February 2002 / Accepted: 27 March 2002     

Pectin-fermenting Bacteria Isolated from the Bovine Rumen

Thirty-two strains of pectin-fermenting rumen bacteria were isolated from bovine rumen contents in a rumen fluid medium which contained pectin as the only added energy source. Based on differences in morphology and the Gram stain, 10 of these strains were selected for characterization. Two strains were identified as Lachnospira multiparus, four strains were identified as Butyrivbrio fibrisolvens, and three strains were identified as Bacteroides ruminicola. Characteristics of the remaining strain did not correspond with any previously described species. It was a gram-positive anaerobic coccus, 1.0 to 1.2 mum in diameter, and occurred primarily as single cells or diplococci. The strain fermented pectin rapidly but showed little or no growth on any other energy sources tested. The only detectable end products were acetic acid and gas, a portion of which was identified as hydrogen. Although the physiological characteristics of this organism differ markedly from other described species, it has been placed in the genus Peptostreptococcus on the basis of morphology, Gram stain, relations to oxygen, and the occurrence of cell division in only one plane. End products of fermentation are somewhat similar to those of the cellulolytic ruminococci. Eight previously characterized strains of cellulolytic bacteria isolated in nonselective media were unable to ferment pectin, whereas ten strains of hemicellulolytic rumen bacteria, eight of which were isolated with a xylan medium, showed considerable variation in this characteristic.     

A Method for Selection and Characterization of Rhizosphere-Competent Bacteria of Chickpea

A greenhouse assay was developed to evaluate the root-colonizing capability of the native chickpea rhizospheric bacterial population. In this assay system, screening time was reduced on two counts. First, spontaneous chromosomal rifampicin-resistant (Rif^r) strains were directly inoculated to seeds without any check for the stability of the mutation, and second, no attempts were made to taxonomically identify all the strains being screened for chickpea rhizosphere competence. Only two chickpea rhizosphere-competent Rif^r strains from the group of six good chickpea rhizosphere colonizers forming 10⁷ to 10⁸ colony-forming units (cfu)/g root were taxonomically identified as Pseudomonas fluorescens NB13R and Pseudomonas spp. NB49R, after screening 49 bacteria. Both the strains showed no difference from their corresponding wild-type strains P. fluorescens NB13 and Pseudomonas spp. NB49 in terms of chickpea rhizosphere competence. Isogenic or equally rhizospheric competitive second non-isogenic bacterial isolate, when present in tenfold higher amount, pre-empted the colonization of the soil by the bacterium, which was present in smaller ratio. These findings indicate that the isogenic or equally rhizospheric competitive second non-isogenic Rif^r strains should be compared for their survival and competition with that of the isogenic parent and with each other for specific ecological niche, before using a mixture of isolates, for stable and consistent biological seed treatment to control soilborn pathogens or pests or to promote plant growth. Received: 31 May 1996 / Accepted: 5 July 1996     

Characterization and Antibacterial Activity Against Helicobacter pylori of Lactic Acid Bacteria Isolated from Thai Fermented Rice Noodle

Probiotics and Antimicrobial Proteins - A total of 32 lactic acid bacteria (LAB) were isolated from Khanom-jeen, a Thai traditional fermented rice noodle. They belonged to the genus Leuconostoc...     

Studies on the Bacteria Isolated from Wine

The growth factor for malo-lactic fermentation bacteria was partially purified from tomato juice, and some properties of the factor were examined. The factor was comparatively a low molecule, thermo-stable and insoluble in nonpolar organic solvents. The purified factor fraction showed positive reaction with Molisch-, tetrazolium- and Nessler-reagents, suggesting the existence of sugar and nitrogen as the chemical components. The treatment with cellobiase or cellulase-II resulted in the inactivation of the factor and simultaneously released the sugar constituent composed of glucose from the factor. These results indicated that the glucose residue might exist as the β-1,4-glucosidic linkage in the growth factor.     

Functional Characterization of Bacteria Isolated from Ancient Arctic Soil Exposes Diverse Resistance Mechanisms to Modern Antibiotics

Using functional metagenomics to study the resistomes of bacterial communities isolated from different layers of the Canadian high Arctic permafrost, we show that microbial communities harbored diverse resistance mechanisms at least 5,000 years ago. Among bacteria sampled from the ancient layers of a permafrost core, we isolated eight genes conferring clinical levels of resistance against aminoglycoside, β-lactam and tetracycline antibiotics that are naturally produced by microorganisms. Among these resistance genes, four also conferred resistance against amikacin, a modern semi-synthetic antibiotic that does not naturally occur in microorganisms. In bacteria sampled from the overlaying active layer, we isolated ten different genes conferring resistance to all six antibiotics tested in this study, including aminoglycoside, β-lactam and tetracycline variants that are naturally produced by microorganisms as well as semi-synthetic variants produced in the laboratory. On average, we found that resistance genes found in permafrost bacteria conferred lower levels of resistance against clinically relevant antibiotics than resistance genes sampled from the active layer. Our results demonstrate that antibiotic resistance genes were functionally diverse prior to the anthropogenic use of antibiotics, contributing to the evolution of natural reservoirs of resistance genes.     

Evaluation of Malolactic Bacteria Isolated from Oregon Wines

Oregon is a cool wine-producing region where grapes characteristically contain high concentrations of organic acids. To reduce the natural acidity and increase the microbiological stability and flavor complexity of the wine, malolactic fermentation is encouraged. In this study, strains of Leuconostoc oenos indigenous to Oregon wines were evaluated for their suitability to conduct malolactic fermentation in Oregon wines. Tests determined the malolactic activity of the Oregon isolates in comparison with commercial strains ML-34, PSU-1, MLT-kli, and ens 44-40 under various temperature and pH conditions. Sensitivities to sulfur dioxide, ethanol, and fumaric acid also were determined. Two Oregon strains, Er-1a and Ey-2d, were selected for commercial winemaking tests because they had greater malolactic activity under conditions of low pH (3.0) and low temperature (15 and 8°C), respectively.