Characterisation and identification of two novel species of sulphate-reducing bacteria from marine environments.
This study describes the characterisation and identification of two species of sulphate-reducing bacteria
isolated from marine environments. The isolate coded Ind 1 was recovered from the heavily corroded hull
of an oil storage vessel moored off the Indonesian coast. An isolate, referred to as Al 1, originated from a
soured oil reservoir in Alaska. Observations using microscopy (light, scanning electron and atomic force)
revealed that cells were Gram-negative, rod-shaped and very motile. Physiological characterisation,
analysis of the fatty acid profiles and partial and full 16S rRNA sequencing demonstrated strong
similarities between the two species and members of the Desulfovibrio genus. The position of the strains
within phylogenetic trees showed Al 1 clustering closely with Desulfovibrio vietnamensis. Ind 1 revealed
a high degree of similarity with both Desulfovibrio gigas and Desulfovibrio gabonensis and these three
strains formed a separate cluster in the delta subdivision of the Proteobacteria. However, whole-cell
protein profiles and Fourier-transform infrared spectroscopy studies showed that there is enough
dissimilarity between the two isolates and the remaining species of the genus Desulfovibrio to consider Al
1 and Ind 1 as new separate species.
Purification, physico-chemical and spectroscopic characterisation of the key enzymes involved in the
sulphate metabolism was carried out for both isolates. Nuclear magnetic resonance and electron
paramagnetic resonance studies revealed that the proteins of Al 1 and Ind 1 exhibited various features in
common with their counterparts from other members of the genus Desulfovibrio. In particular, proteins
from Ind 1 showed many similarities with the enzymes previously described for D. gigas.
Based on the obtained results, the classification of Ind 1 as Desulfovibrio indonensiensis sp. nov. and
Al 1 as Desulfovibrio alaskensis sp. nov. are proposed.
The overall results highlight the complexity of the relationship between cell physiology and the
organisms' environmental impact.