Brevibacterium casei

Abstract: The molecular diversity of aerobic endospore-forming bacteria, typically Bacillus and its derived genera, has been investigated in various environments. However, there have been few investigations concerning Bacillus in acidic soils. In this study, the genotypic diversity and phylogenetic relationships among plant growth-promoting (PGP) bacilli isolated from the rice rhizosphere growing in acidic soils of Kerala (pH varying from 6.3 to 6.8) were investigated. For assessing their biocontrol potential and PGP attributes, 115 isolates were randomly selected and 49 isolates that were positive for multiple traits were selected. Metabolic characterization of representative strains, using the Biolog GP2 (Gram Positive) MicroPlate(TM) , revealed a large versatility with respect to carbohydrate utilization. Amplified ribosomal DNA restriction analysis revealed 13 clusters at 65% similarity level, which consisted of 1-21 strains. 16S rDNA partial sequencing assigned all the isolates, except for one, to the Bacillus genus, with close relatedness to Bacillus humi, B. megaterium, B. drentensis, B. pocheonensis, B. aestuarii, B. arbutinivorans, B. niacini, and Brevibacterium casei. The Bacillus species with different metabolic capabilities, PGP abilities, and genetic diversity found in this study are likely to have ecological relevance.

Abstract: Diverse methylotrophic bacteria were isolated from the tongue, and supra- and subgingival plaque in the mouths of volunteers and patients with periodontitis. One-carbon compounds such as dimethylsulfide in the mouth are likely to be used as growth substrates for these organisms. Methylotrophic strains of Bacillus, Brevibacterium casei, Hyphomicrobium sulfonivorans, Methylobacterium, Micrococcus luteus and Variovorax paradoxus were characterized physiologically and by their 16S rRNA gene sequences. The type strain of B. casei was shown to be methylotrophic. Enzymes of methylotrophic metabolism were characterized in some strains, and activities consistent with growth using known pathways of C1-compound metabolism demonstrated. Genomic DNA from 18 tongue and dental plaque samples from nine volunteers was amplified by the polymerase chain reaction using primers for the 16S rRNA gene of Methylobacterium and the mxaF gene of methanol dehydrogenase. MxaF was detected in all nine volunteers, and Methylobacterium was detected in seven. Methylotrophic activity is thus a feature of the oral bacterial community.

Abstract: Environmental pollution by heavy metals has become a serious problem in the world. Phytoextraction, which is one of the plant-based technologies, has attracted the most attention for the bioremediation of soils polluted with these contaminants. The aim of this study was to determine whether the multiple-tolerant bacterium, Brevibacterium casei MH8a isolated from the heavy metal-contaminated rhizosphere soil of Sinapis alba L., is able to promote plant growth and enhance Cd, Zn and Cu uptake by white mustard under laboratory conditions. Additionally, the ability of the rifampicin-resistant spontaneous mutant of MH8a to colonize plant tissues and its mechanisms of plant growth promotion were also examined. In order to assess the ecological consequences of bioaugmentation on autochthonous bacteria, the phospholipid fatty acid (PLFA) analysis was used. The MH8a strain exhibited the ability to produce ammonia, 1-amino-cyclopropane-1-carboxylic acid deaminase, indole 3-acetic acid and HCN but was not able to solubilize inorganic phosphate and produce siderophores. Introduction of MH8a into soil significantly increased S. alba biomass and the accumulation of Cd (208%), Zn (86%) and Cu (39%) in plant shoots in comparison with those grown in non-inoculated soil. Introduced into the soil, MH8a was able to enter the plant and was found in the roots and leaves of inoculated plants thus indicating its endophytic features. PLFA analysis revealed that the MH8a that was introduced into soil had a temporary influence on the structure of the autochthonous bacterial communities. The plant growth-promoting features of the MH8a strain and its ability to enhance the metal uptake by white mustard and its long-term survival in soil as well as its temporary impact on autochthonous microorganisms make the strain a suitable candidate for the promotion of plant growth and the efficiency of phytoextraction.