The Cyst-Dividing Bacterium Ramlibacter tataouinensis TTB310 Genome Reveals a Well-Stocked Toolbox for Adaptation to a Desert Environment

Ramlibacter tataouinensis TTB310T (strain TTB310), a betaproteobacterium isolated from a semi-arid region of South Tunisia (Tataouine), is characterized by the presence of both spherical and rod-shaped cells in pure culture. Cell division of strain TTB310 occurs by the binary fission of spherical “cyst-like” cells (“cyst-cyst” division). The rod-shaped cells formed at the periphery of a colony (consisting mainly of cysts) are highly motile and colonize a new environment, where they form a new colony by reversion to cyst-like cells. This unique cell cycle of strain TTB310, with desiccation tolerant cyst-like cells capable of division and desiccation sensitive motile rods capable of dissemination, appears to be a novel adaptation for life in a hot and dry desert environment. In order to gain insights into strain TTB310's underlying genetic repertoire and possible mechanisms responsible for its unusual lifestyle, the genome of strain TTB310 was completely sequenced and subsequently annotated. The complete genome consists of a single circular chromosome of 4,070,194 bp with an average G+C content of 70.0%, the highest among the Betaproteobacteria sequenced to date, with total of 3,899 predicted coding sequences covering 92% of the genome. We found that strain TTB310 has developed a highly complex network of two-component systems, which may utilize responses to light and perhaps a rudimentary circadian hourglass to anticipate water availability at the dew time in the middle/end of the desert winter nights and thus direct the growth window to cyclic water availability times. Other interesting features of the strain TTB310 genome that appear to be important for desiccation tolerance, including intermediary metabolism compounds such as trehalose or polyhydroxyalkanoate, and signal transduction pathways, are presented and discussed

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Production of auxin and other indolic and phenolic compounds by <em>Paenibacillus polymyxa</em> strains isolated from different proximity to plant roots.

We determined the actual (no tryptophan, Trp, addition) and potential (Trp 0.1 g l(-1) added) production of indolic and phenolic compounds produced in different culture media by Paenibacillus polymyxa strains which had been isolated from different proximity to wheat roots. The production of indole-3-acetic acid (IAA) and related indolic metabolites by all strains tested was greatly enhanced upon Trp addition, suggesting that Trp is important as IAA precursor. A gradual decrease in potential IAA and an increase in potential indole-3-ethanol and indole-3-lactic acid production by strains isolated from non-rhizosphere soil (NRS) over rhizosphere soil (RS) to the rhizoplane (RP) were obtained. The NRS strain showed also a higher (potential) production of oxidized compounds such as indole-3-carboxylic and benzoic acid besides IAA. The determined metabolic differences indicate together with previous results on genetic and physiological parameters of P. polymyxa populations that plant roots select different P. polymyxa subpopulations. Our results suggest that the selected genotypes are differentially adapted to the decreasing oxygen pressure from NRS to RP. Possible effects of the probably microhabitat-specific metabolic profiles of the P. polymyxa isolates for plant growth are discussed

Dynamics of the diazotroph Bacillus polymyxa in the rhizosphere of wheat (Triticum aestivum L.)after inoculation and its effect on uptake of 15 N-labelled fertilizer

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The genotypic diversity of Pseudomonas brassicacearum populations isolated from roots of Arabidopsis thaliana: influence of plant genotype

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Structural analysis of the exopolysaccharide from Burkholderia caribensis strain MWAP71

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