RESUMEN
A new member of the genus Thiomicrospira, which utilizes thiosulfate as the electron donor and CO2 as the carbon source, was isolated from a sediment sample dominated by the filamentous sulfur bacterium Thioploca. Although the physiological properties investigated are nearly identical to other described species of the genus, it is proposed that strain Ch-1T is a member of a new species, Thiomicrospira chilensis sp. nov., on the basis of differences in genotypic characteristics (16S rRNA sequence, DNA homology, G + C content). Strain Ch-1T was highly motile with a slight tendency to form aggregates in the stationary growth phase. The organism was obligately autotrophic and strictly aerobic. Nitrate was not used as an electron acceptor. Chemolithoautotrophic growth was observed with thiosulfate, tetrathionate, sulfur and sulfide. The isolate was not able to grow heterotrophically. Growth of strain Ch-1T was observed between pH 5.3 and 8.5 with an optimum at pH 7.0. The temperature range for growth was between 3.5 and 42 degrees C; the optimal growth temperature was between 32 and 37 degrees C. The mean maximum growth rate on thiosulfate was 0.4 h-1. This is the second Thiomicrospira species described that has a rod-shaped morphology; therefore discrimination between vibrio-shaped Thiomicrospira and rod-shaped Thiobacilli is no longer valid.
Asunto(s)
Sedimentos Geológicos/microbiología , Bacterias Gramnegativas Quimiolitotróficas/clasificación , Azufre/metabolismo , Microbiología del Agua , Composición de Base , ADN Bacteriano/química , ADN Bacteriano/genética , ADN Ribosómico/química , ADN Ribosómico/genética , Genes de ARNr , Bacterias Gramnegativas Quimiolitotróficas/aislamiento & purificación , Bacterias Gramnegativas Quimiolitotróficas/fisiología , Datos de Secuencia Molecular , Hibridación de Ácido Nucleico , Oxidación-Reducción , ARN Ribosómico 16S/genética , Ribulosa-Bifosfato Carboxilasa/metabolismoRESUMEN
Our basic microbiological studies of the water column and the sediment of Golfo Dulce, Costa Rica, were focused on aerobic and denitrifying sulfur-oxidizing bacteria and anaerobic sulfate-reducing bacteria. We observed no increasing numbers of total bacterial counts within the water column. Although no oxygen was present hydrogen sulfide was only detectable close to the sediment. The highest numbers of sulfate-reducing bacteria measured by Most-Probable-Number counts were found in or close to the sediment. In the anoxic bottom water sulfide-oxidizing bacteria typically containing large sulfur globules were observed microscopically. They were identified as free-swimming Thiovulum and Thiospira species. At one station large vacuolated forms of the filamentous colourless sulfur bacterium Beggiatoa were noted. Together with these sulfur containing bacteria there were long free swimming rods showing no sulfur inclusions of unknown character. The microscopic observations showed good correlation with Most-Probable-Number-counts and molecular biological techniques for sulfate-reducing bacteria.