Thiorhodococcus fuscus sp. nov., isolated from a lagoon.

Area of Science:

• Microbiology
• Bacteriology
• Photosynthetic bacteria

Background:

• Sediment samples from Chilika lagoon, India, were used for microbial enrichment.
• A photoheterotrophic enrichment culture yielded a novel bacterium, strain JA363T.

Purpose of the Study:

• To isolate, characterize, and phylogenetically classify a novel bacterium from Chilika lagoon.
• To determine the taxonomic position of strain JA363T within the genus Thiorhodococcus.

Main Methods:

• Isolation and purification of strain JA363T.
• Morphological, physiological, and biochemical characterization.
• Analysis of major fatty acids, polar lipids, and quinone systems.
• Phylogenetic analysis based on 16S rRNA gene sequences.

Main Results:

• Strain JA363T is a brown, moderately halophilic, photoautotrophic, Gram-negative coccoid bacterium with a single polar flagellum.
• It requires NaCl, tolerates up to 7% NaCl, and possesses complex growth factor requirements.
• Photosynthetic pigments include bacteriochlorophyll a and spirilloxanthin series carotenoids (rhodopin >85%).
• Major fatty acids are C16:1ω7c/C16:1ω6c, C18:1ω7c, and C16:0; major polar lipids are phosphatidylglycerol and phosphatidylethanolamine; Q8 is the predominant quinone.
• Phylogenetic analysis of 16S rRNA gene sequences showed highest similarity to Thiorhodococcus kakinadensis (98.7%).
• Phylogenetic trees and chemotaxonomic data support placement within the genus Thiorhodococcus.

Conclusions:

• Strain JA363T represents a novel species within the genus Thiorhodococcus.
• The novel species is named Thiorhodococcus fuscus sp. nov., with strain JA363T as the type strain.