Summary auto-generated
This study describes the characterization and identification of two butane-utilizing bacterial strains, IMT37T and IMT40, isolated from oilfield soils in Gujarat, India. Using a polyphasic approach, researchers confirmed these strains belong to the genus Pseudomonas but represent a novel species. Biochemical and physiological tests showed both strains are Gram-negative, aerobic, motile rods with single polar flagella capable of utilizing gaseous butane, higher alkanes, and various organic compounds as carbon sources. Fatty acid analysis revealed profiles most similar to Pseudomonas mendocina. DNA-DNA hybridization studies demonstrated 88-100% relatedness between the two strains but only 49-71% relatedness to seven established Pseudomonas species, with high ∆Tm values (11.5-19°C) indicating significant base-pair mismatches. The 16S rRNA gene sequencing confirmed their placement within authentic Pseudomonas (γ-Proteobacteria) but showed less than 96% sequence similarity to known species. Notably, the DNA G-C content was 72 mol%, the highest reported for Pseudomonas. Based on these molecular and phenotypic data, the authors propose the novel species Pseudomonas indica sp. nov., with IMT37T as the type strain.
Key findings
- Two strains (IMT37T and IMT40) isolated from oilfields are the first authentic Pseudomonas species documented to utilize gaseous butane as sole carbon and energy source
- DNA-DNA hybridization showed 88-100% relatedness between the two strains but only 49-71% relatedness to established Pseudomonas species, with ∆Tm values exceeding the 5°C threshold for species differentiation
- 16S rRNA gene sequences showed 99% similarity between the two strains but less than 96% similarity to all known Pseudomonas species, placing them in a novel phylogenetic cluster
- The strains possess the highest G-C content (72 mol%) reported for any Pseudomonas species
- The novel species Pseudomonas indica sp. nov. is proposed with strain IMT37T (MTCC 3713T, DSM 14015T) designated as the type strain
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Abstract
The taxonomic position of two butane-utilizing bacteria was studied using a polyphasic approach. Biochemical and physiological characteristics indicated these to be members of the genus Pseudomonas, showing more similarity to Pseudomonas mendocina than to any other species. The major fatty acids found in these two strains also pointed to their similarity to P. mendocina. On the other hand, DNA--DNA hybridization studies with seven related Pseudomonas species belonging to the gamma-Proteobacteria and the DeltaT(m) values of reassociated molecules clearly showed that these two strains do not belong to any of the seven species tested. The 16S rRNA gene was sequenced and compared with the sequences available in the GenBank database. Phylogenetic analysis using the region covering positions 31--1488 (Escherichia coli numbering) confirmed these observations and placed these two strains as members of the authentic Pseudomonas, but not in any existing species of the genus. On the basis of biochemical characteristics, fatty acid profiles, DNA--DNA reassociation and DeltaT(m) values, as well as 16S rRNA gene sequence analyses, these two isolates were shown to belong to one species but to have characteristics distinct from those of validly described species of Pseudomonas (sensu stricto). These strains, therefore, should be recognized as a novel species, for which the name Pseudomonas indica sp. nov. is proposed. The type strain is strain IMT37(T) (=MTCC 3713(T)=DSM 14015(T)).