RESUMEN

We screened soil samples for CO(2)-requiring extreme oligotrophs similar to Rhodococcus erythropolis N9T-4, which can grow on a basal salt agar medium without an organic carbon source. From 387 soil samples, three isolates were obtained and identified as Streptomyces spp. by 16S rDNA analysis. The isolates required gaseous CO(2) for growth and grew on a basal salt medium solidified by silica gel. These results suggest that such CO(2)-requiring oligotrophs occur widely in nature.

Asunto(s)

Dióxido de Carbono/metabolismo , Microbiología del Suelo , Streptomyces/aislamiento & purificación , Streptomyces/metabolismo , Técnicas de Tipificación Bacteriana , Secuencia de Bases , Medios de Cultivo , ADN Bacteriano/análisis , ADN Ribosómico/análisis , Datos de Secuencia Molecular , ARN Ribosómico 16S/genética , Streptomyces/genética

RESUMEN

Rhodococcus erythropolis N9T-4, which was isolated from crude oil, showed extremely oligotrophic growth and formed its colonies on a minimal salt medium solidified using agar or silica gel without any additional carbon source. N9T-4 did not grow under CO(2)-limiting conditions but could grow on a medium containing NaHCO(3) under the same conditions, suggesting that the oligotrophic growth of N9T-4 depends on CO(2). Proteomic analysis of N9T-4 revealed that two proteins, with molecular masses of 45 and 55 kDa, were highly induced under the oligotrophic conditions. The primary structures of these proteins exhibited striking similarities to those of methanol: N,N'-dimethyl-4-nitrosoaniline oxidoreductase and an aldehyde dehydrogenase from Rhodococcus sp. These enzyme activities were three times higher under oligotrophic conditions than under n-tetradecane-containing heterotrophic conditions, and gene disruption for the aldehyde dehydrogenase caused a lack of growth on the minimal salt medium. Furthermore, 3-hexulose 6-phosphate synthase and phospho-3-hexuloisomerase activities, which are key enzymes in the ribulose monophosphate pathway in methylotrophic bacteria, were detected specifically in the cell extract of oligotrophically grown N9T-4. These results suggest that CO(2) fixation involves methanol (formaldehyde) metabolism in the oligotrophic growth of R. erythropolis N9T-4.

Asunto(s)

Petróleo/microbiología , Rhodococcus/crecimiento & desarrollo , Rhodococcus/metabolismo , Oxidorreductasas de Alcohol/genética , Oxidorreductasas de Alcohol/metabolismo , Aldehído Oxidorreductasas/genética , Aldehído Oxidorreductasas/metabolismo , Secuencia de Aminoácidos , Dióxido de Carbono/metabolismo , Electroforesis en Gel Bidimensional , Regulación Bacteriana de la Expresión Génica , Modelos Biológicos , Datos de Secuencia Molecular , ARN Ribosómico 16S/genética , Rhodococcus/genética , Análisis de Secuencia de ADN