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A Gram-negative, mesophilic bacterial strain, designated 1-1B T , which degrades polycyclic aromatic hydrocarbons, was isolated from petroleum-contaminated seawater during a bioremediation experiment. A 16S rRNA gene sequence analysis indicated that the isolate was affiliated with the genus Thalassospira in the Alphaproteobacteria; the sequence was found to be most similar to those of Thalassospira profundimaris WP0211 T (99.8 %), Thalassospira xiamenensis M-5 T (98.2 %) and Thalassospira lucentensis DSM 14000 T (98.1 %). However, the levels of DNA-DNA relatedness between strain 1-1B T and these type strains were 50.7±17.2, 35.7±17.8 and 32.0±21.1 %, respectively. In addition, strain 1-1B

Biological soil disinfestation (BSD) using plant biomass incorporation is an effective method and a good alternative to chemical fumigants for controlling soil-borne plant pathogens. In this study the bacterial communities in pot soil treated with three different BSD conditions (without plant biomass and with Brassica juncea L. plants or bran of wheat, Triticum aestivum L.) were analyzed using mainly molecular techniques. Earlier dropping of redox potential of both biomass-treated soils indicated rapid development of anaerobic conditions in the soil. The population of Fusarium oxysporum F. pathogen incorporated in the soil at the start was decreased considerably during the treatment, and the number of culturable anaerobic bacteria increased in both biomass-treated soils. Rather high concentrations of acetate and butyrate were detected from the biomass-treated soils. The polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis for the V3 region of 16S rRNA gene sequences revealed that the profiles of both biomass-treated soils were initially represented by similar and dominant groups, many of which were closely related to the species in the classes Clostridia and Bacilli of the phylum Firmicutes. Based on the clone library analysis, the control soil samples showed diverse bacterial groups with a few number of anaerobic clones. In contrast, for both biomass-treated libraries, clones belonging to the class Clostridia, a strictly anaerobic spore-forming bacterial group, appeared exceedingly dominant. The clostridial group detected was composed of phylogenetically diverse members, and it seemed likely that the diverse clostridial species were responsible for suppression of pathogens by making various compounds including volatile fatty acids and other compounds during anaerobic decomposition of plant biomass.

Culturable anaerobic bacterial populations on rice plant residue (straw and stubble with roots) in paddy field soil were found on the order of 10(9) CFU (colony-forming units) (g dry weight of plant residue)(-1), and the percentages of spores were usually less than 1% of the total anaerobes. Anaerobic bacteria were isolated from each sample by picking up colonies on the roll tube agar used for the enumeration. The phylogenetic analysis of 47 isolates based on 16S rRNA gene sequences revealed that the composition of dominant culturable anaerobic bacteria on rice plant residue was rather simple. The most dominant group was closely related to the Cellulomonas species in the Actinobacteria phylum and accounted for more than 60% of the isolates for most of the samples. The second major group was also affiliated with the Actinobacteria phylum and tentatively named the 'propionate-producing Actinobacteria group' because the strains in the group commonly produced propionate. Strains in the third group, the 'Prevotella-like group', were Gram-negative, strictly anaerobic rods and placed in the Bacteroides phylum with 16S rRNA gene similarities of 86-92% to the closest relatives. Some other strains belonging to Betaproteobacteria and the clostridial group were also isolated. Most of the strains affiliated to the clostridial group were isolated from the heat-treated samples. Some phenotypic characteristics of representative strains of each group are also described.