The phylogenetic affiliations of organisms responsible for aerobic CO oxidation in hypersaline soils and sediments were assessed using media containing 3.8 M NaCl. CO-oxidizing strains of the euryarchaeotes, Haloarcula, Halorubrum, Haloterrigena and Natronorubrum, were isolated from the Bonneville Salt Flats (UT) and Atacama Desert salterns (Chile). A halophilic euryarchaeote, Haloferax strain Mke2.3(T), was isolated from Hawai'i Island saline cinders. Haloferax strain Mke2.3(T) was most closely related to Haloferax larsenii JCM 13917(T) (97.0% 16S rRNA sequence identity). It grew with a limited range of substrates, and oxidized CO at a headspace concentration of 0.1%. However, it did not grow with CO as a sole carbon and energy source. Its ability to oxidize CO, its polar lipid composition, substrate utilization and numerous other traits distinguished it from H. larsenii JCM 13917(T), and supported designation of the novel isolate as Haloferax namakaokahaiae Mke2.3(T), sp. nov (= DSM 29988, = LMG 29162). CO oxidation was also documented for 'Natronorubrum thiooxidans' HG1 (Sorokin, Tourova and Muyzer 2005), N. bangense (Xu, Zhou and Tian 1999) and N. sulfidifaciens AD2(T) (Cui et al. 2007). Collectively, these results established a previously unsuspected capacity for extremely halophilic aerobic CO oxidation, and indicated that the trait might be widespread among the Halobacteriaceae, and occur in a wide range of hypersaline habitats.
Rhizobacteria with biocontrol ability exploit a range of mechanisms to compete successfully with other microorganisms and to ensure their growth and survival in the rhizosphere, ultimately promoting plant growth. The rhizobacterium Serratia plymuthica AS13 is able to promote oilseed rape growth and improve seedling survival in the presence of the fungal pathogen, Rhizoctonia solani AG 2-1; however, our understanding of the mechanisms underlying the antagonism of Serratia is limited. To elucidate possible mechanisms, genome-wide gene expression profiling of S. plymuthica AS13 was carried out in the presence or absence of R. solani. We used RNA sequencing methodology to obtain a comprehensive overview of Serratia gene expression in response to R. solani. The differential gene expression profiles of S. plymuthica AS13 revealed significantly increased expression of genes related to the biosynthesis of the antibiotic pyrrolnitrin (prnABCD), protease production and transporters. The results presented here provide evidence that antibiosis is a major functional mechanism underlying the antagonistic behaviour of S. plymuthica AS13.
A plant-associated member of the family Enterobacteriaceae, Serratia plymuthica strain AS12 was isolated from rapeseed roots. It is of scientific interest because it promotes plant growth and inhibits plant pathogens. The genome of S. plymuthica AS12 comprises a 5,443,009 bp long circular chromosome, which consists of 4,952 protein-coding genes, 87 tRNA genes and 7 rRNA operons. This genome was sequenced within the 2010 DOE-JGI Community Sequencing Program (CSP2010) as part of the project entitled “Genomics of four rapeseed plant growth promoting bacteria with antagonistic effect on plant pathogens”.
Serratia plymuthica are plant-associated, plant beneficial species belonging to the family Enterobacteriaceae. The members of the genus Serratia are ubiquitous in nature and their life style varies from endophytic to free-living. S. plymuthica AS9 is of special interest for its ability to inhibit fungal pathogens of rapeseed and to promote plant growth. The genome of S. plymuthica AS9 comprises a 5,442,880 bp long circular chromosome that consists of 4,952 protein-coding genes, 87 tRNA genes and 7 rRNA operons. This genome is part of the project entitled “Genomics of four rapeseed plant growth promoting bacteria with antagonistic effect on plant pathogens” awarded through the 2010 DOE-JGI Community Sequencing Program (CSP2010).
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