Summary auto-generated
Flavobacterium frigidarium sp. nov. is a novel psychrophilic bacterium isolated from marine sediment near Adelaide Island, Antarctica. This aerobic, non-motile, Gram-negative rod exhibits remarkable enzymatic capabilities, notably xylanolytic and laminarinolytic activities—the latter representing the first reported aerobic, psychrophilic laminarinolytic bacterium. The organism is yellow-pigmented, produces extracellular galactosamine glycan, and contains the carotenoid zeaxanthin. It grows optimally at 15°C on xylan medium with doubling times of 9.6 hours, but can also grow at 0°C. The bacterium is halotolerant and neutrophilic, with optimal growth at pH 7.5. Analysis of 16S rRNA gene sequences places it within the genus Flavobacterium with 96.8% similarity to the closest relative, Flavobacterium columnare, but DNA-DNA hybridization confirms it represents a distinct species with only 35.7% genomic similarity to F. hydatis. The genomic DNA has 35 mol% G+C content. Membrane analysis reveals characteristic polyunsaturated branched-chain fatty acids typical of psychrophilic bacteria. Both xylanase and laminarinase enzymes demonstrate cold-active properties with greater catalytic activity below 20°C and reduced thermostability at elevated temperatures.
Key findings
- Flavobacterium frigidarium is the first described aerobic, psychrophilic laminarinolytic bacterium, representing a novel species isolated from Antarctic marine sediment
- The bacterium exhibits cold-active xylanase and laminarinase enzymes with greater catalytic activity at temperatures below 20°C and reduced thermostability compared to mesophilic counterparts
- Growth optimal at 15°C with doubling time of 9.6 hours, capable of growth at 0°C with doubling time of 34.8 hours, and maximum growth at 24°C
- 16S rRNA sequence analysis shows 96.8% similarity to Flavobacterium columnare but DNA-DNA hybridization confirms novel species status with only 35.7% genomic DNA similarity to closest relatives
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Abstract
A psychrophilic, aerobic bacterium designated A2i(T) was isolated from marine sediment recovered from shallow waters surrounding Adelaide Island, Antarctica (67 degrees 34' S, 68 degrees 07' W). The organism exhibited xylanolytic and laminarinolytic activity and was halotolerant. Basic characterization showed that it was Gram-negative, non-motile, yellow-pigmented (beta,beta-carotene-3,3'-diol) and positive for oxidase and catalase synthesis. Analysis of the 16S rDNA sequence suggests that the organism belongs to the Flexibacter--Cytophaga--Bacteroides phylum. On the basis of its 16S rDNA sequence, the bacterium is 96.8% similar to Flavobacterium columnare ATCC 43622 -- its closest relation. The genomic DNA G+C content was 35 mol%. Growth on xylan occurs optimally at 15 degrees C, though growth also occurs at 0 degrees C, and the doubling times are 9.6 and 34.8 h, respectively. The maximum growth temperature on xylan is at 24 degrees C. The bacterium is a neutrophile, growing across the pH range 5.6--8.4 and having an optimum at pH 7.5. Analysis of the 16S rDNA sequence, together with phenotypic characterization, suggests that the organism is a member of the genus Flavobacterium. DNA--DNA hybridization experiments have shown that it is a novel species; it is proposed, therefore, that the organism be designated as the type strain of Flavobacterium frigidarium sp. nov. (=ATCC 700810(T)=NCIMB 13737(T)).