Agromonas oligotrophica is an oligotrophic, dinitrogen-fixing soil bacterium which is found to grow on ferulic acid.This study aimed to characterize in more detail the growth of A.oligotrophica on ferulate and the degradation of ferulate.Ten- and 100-fold dilutions of conventional nutrient broth(NB/10 and NB/100, respectively) and yeast extract-supplemented mineral salts(MS) media were used for the batch growth experiments.In these media, the initial growth of A.oligotrophica was suppressed by ferulate in a dose-dependent manner.However, the cell biomass formed in the cultures was positively correlated with the amounts of ferulate used at ferulate concentrations between 0 and 5mM, indicating that ferulate was the growth-limiting nutrient under the conditions.Thus, the growth yield on ferulate was calculated to be 59-67g dry weight(mol ferulate)-1 in the NB/10 and the yeast extract-supplemented MS cultures, while in the NB/100 cultures a lower value [33g dry weight(mol ferulate)-1] was obtained.In a resting cell experiment with ferulate, vanillate was identified by high performance liquid chromatography and the degradation pathway was expected to be analogous to the well-known pathway which includes vanillate and protocatechuate as intermediates.
Microbial biomass C and N, dehydrogenase and nitrifying activities were measured together with other physicochemical parameters of soil such as the three phase distributions, and the amounts of soil organic matter, mineralizable carbon and nitrogen, in a 100cm deep Andosol profile in an arable field in Matsudo city, central Japan.In the three phase distributions of soil, the solid phase was:5-10cm=15-20cm>55-60cm>35-40cm=75-80cm.Total organic C and N were highest at 15-20cm(40.4 and 2.8mg kg-1, respectively) and decreased with depth, being lowest at 75-80cm(18.6 and 0.6mg kg-1, respectively).Available P and ammonium N followed the same trend as total organic C and N.However, nitrate N was highest at 35-40cm(51.6mg kg-1 soil)and lowest at 5-10cm(19.1mg kg-1 soil).Microbial biomass C and N were highest at 15-20cm(202 and 26mg kg-1 soil, respectively), and showed a tendency to decrease with depth.Mineralizable C and N followed the same trend as microbial biomass C and N and were found to have the lowest values at 75-80cm.Dehydrogenase activity was highest at 15-20cm and much lower below this depth(51.2 and 3.3-3.7μg Triphenyl formazan g-1 soil 24hr-1, respectively) and was highly correlated with soil microbial biomass(r2=0.922, P<0.05).Nitrifying activity was also highest at 15-20cm and decreased with depth to a low at 75-80cm.These properties are important to understanding N dynamics in an Andosol profile, especially the mechanism of nitrate leaching from an arable field to ground water.
Characteristics and propionate production of propionate-producing becteria in an anaerobic digester were examined.Strains VA-1, MC-1 and KA-2 isolated from sludge were nonmotile, nonspore forming, gram-positive and pleomorphic rods.They fermented lactate to propionate and acetate both with a complex medium and with a mineral medium.The molar ratio of propionate to acetate was 2/1.They utilized glucose, lactate, fumarate, malate, pyruvate and serine for growth, but could not use starch and inulin.From these results the propionate-producing bacteria are considered to be classified into the genus Propionibacterium according to Bergey’s manual of determinative bacteriology.Propionibacterium in methane fermentation sludges may utilize low molecular compounds such as monosaccharides, organic acids and amino acids to produce propionate and acetate.PCR amplification using genus-specific primers supported this identification as Propionibacterium.Lactate was converted to propionate and acetate in the dual culture with Propionibacterium sp.strain VA-1 and Desulfovibrio vulgaris strain F-1 in the presence of sulfate.In the triculture with strain VA-1 and strain F-1 in syntrophic association with Methanobacterium formicicum strain HM-1 in the absence of sulfate, lactate was fermented to propionate, acetate and methane.The molar ratio of propionate to acetate in both mixed cultures decreased by about 1/8 as compared with that of the single culture of strain VA-1.The ratio, however, increased 2/1 in the case of the triculture at pH 5.0.Although the population of Propionibacterium in the dual culture and the triculture at pH 7.0 was large, the amount of propionate produced was not.Because of the slow growth rate of Propionibacterium, the propionate production may increase slowly.Under acidic conditions, propionate produced by Propionibacterium is considered to be accumulated in an anaerobic digester as sulfate reducers and methanogens are not able to grow under the conditions.
We studied calcareous concretions from the Epte river.Two strains, Bacillus sp.and Bacillus licheniformis, were isolated from these concretions.The aim of this study was to follow calcium carbonate formation at the early stages of the mineralizing process and to identify crystals by Fourier transform infrared spectroscopy(FTIRS).Bacillus cereus and Bacillus sp.associated with Bacillus licheniformis were cultured on a calcium-enriched medium.Crystal formation was assessed by sampling at 20 h, 48 h, 72 h, 1 week and 2 weeks.After being picked up from the culture and air dried, crystals were identified by FTIRS.An experiment without bacteria inoculum was performed as control.No crystal was obtained in the control experiment.Crystals were present in all cultures of Bacillus species.We observed several steps in the formation of calcium deposits.In most experiments, vaterite appeared as the initial crystalline phase and was followed by carbapatite as a transient phase.Lastly, calcite crystals appeared in all cases within two weeks.Differences in both kinetics and abundance of minerals were observed depending on the tested strain, Bacillus cereus or Bacillus licheniformis and Bacillus sp.association.FTIRS is a sensitive and suitable technique for studying the early stages of Bacillus-induced crystallization.
The incidence of Salmonella and Escherichia coli in chicken retail outlets in a residential area of Coimbatore, Tamil Nadu, India., was studied with the view that accessories may be a source of cross-contamination.Accessories like cages, knives, chopping boards, weighing balance trays and the hands of the butcher were examined.A total of 14 Salmonella as well as 31 E.coli strains were isolated from different sources.Strains of which 13 were S.enteritidis and 1 was S.cerro.The incidence of E.coli was higher than that of Salmonella.The highest incidence of Salmonella was found in chopping boards and the maximum level of E.coli was detected in cages.Salmonella and E.coli isolates were able to survive on different types of wood and metal surfaces for up to 24 hours at room temperature(28±2°C)without any nutrients.This showed that viable cells of both the bacteria could remain on the surface of the chopping boards, knives and weighing balance trays and cause cross contamination.All the strains of Salmonella and E.coli isolated were examined for resistance against 10 antibiotics.All Salmonella strains were resistant to neomycin, polymyxin-B and tetracycline and more than 90% were resistant to ampicillin. E.coli strains(100%)were found to be resistant to ampicillin, neomycin, polymyxin-B, sulphamethoxazole and tetracycline.Multiple antibiotic resistance indexing of both the strains revealed that they originated from high-risk sources of contamination, where antibiotics were often used.In conclusion, these organisms persist in the outlet for long periods and prevention of cross contamination of chicken meat will be needed.