Afifella aestuarii sp. nov., a phototrophic bacterium.

An oval- to rod-shaped, motile, Gram-stain-negative, oxidase-positive, catalase-negative, pink-coloured phototrophic bacterium (designated as strain JA968T) was isolated from an estuary near Pata, Gujarat, India. Cells had an intracytoplasmic membrane architecture as lamellae and divided by budding. Strain JA968T had bacteriochlorophyll-a and spirilloxanthin series carotenoids as photosynthetic pigments. The strain exhibited photolithoautotrophic, photoorganoheterotrophic and chemoorganoheterotrophic growth modes and required thiamine as a growth factor. Strain JA968T had C18 : 1ω7c/C18  : 1ω6c as the predominant fatty acid with ubiquinone-10 (Q-10) and menaquinone-10 (MK-10) forming the quinone composition. The genomic DNA G+C content of the strain was 63.5 mol%. Pairwise comparison of 16S rRNA gene sequences showed that strain JA968T was highly similar to Afifella marina DSM 2698T (99.9 %) and Afifella pfennigii DSM 17143T (98.4 %). The average nucleotide identity values were 92 % between strain JA968T and A. marina DSM 2698T, and 78 % between strain JA968T and A. pfennigii DSM 17143T. The digital DNA-DNA hybridization values between strain JA968T and A. marina and A. pfennigii were 49 and 19 %, respectively. The genomic distinction was also supported by differences in phenotypic and chemotaxonomic characteristics. We propose that strain JA968T represents a new species of the genus Afifella with the name Afifella aestuarii sp. nov. The type strain is JA968T (=KCTC 15634T=NBRC 113338T).

Diversity and bioprospective potential (cold-active enzymes) of cultivable marine bacteria from the subarctic glacial Fjord, Kongsfjorden.

The diversity and abundance of culturable bacteria in Kongsfjorden water (15 stations) and sediments (12 stations) were studied. Viable numbers ranged between 105­106 CFU l−1 in water and 102­104 CFU g−1 in the sediments. A total of 291 and 43 bacterial isolates were retrieved from the water (KJF) and sediments (FS), respectively. Based on 16S rRNA gene sequence similarities, the KJF and FS isolates were grouped into 49 and 23 phylotypes, respectively. The KJF and FS phylotypes represented three phyla namely, Actinobacteria, Bacteroidetes, and Proteobacteria. At the genus level, Flavobacterium and Shewanella and at the species level, Pseudoaltermonas arctica and Colwellia psychrerythraea were dominant in the water and sediments, respectively. Most phylotypes were psychrotolerant with upper growth temperature limit of 25­37 °C and tolerated 0.3­2.5 M NaCl and pH values of 5.0­11.0. Majority of the phylotypes produced one or more of the extracellular hydrolytic enzymes amylase, lipase, caseinase, urease, gelatinase, and DNase at 4 and 18 °C, while none were chitinolytic. Few of the FS phylotypes exhibited extracellular activity only at 4 or 18 °C. Nine FS and 21 KJF isolates were pigmented. The predominant cellular fatty acids were unsaturated, branched, and modified fatty acids, which are unique to cold-adapted bacteria.

Arcticibacter svalbardensis gen. nov., sp. nov., of the family Sphingobacteriaceae in the phylum Bacteroidetes, isolated from Arctic soil.

In the course of a study aimed at isolating bacteria from Arctic soils by a method that selectively enriches for rare bioactive actinomycetes, a Gram-stain-negative, pigmented, non-motile rod, designated MN12-7(T), was isolated. The salmon-pink strain was, based on 16S rRNA gene sequence similarity, found to be affiliated with the family Sphingobacteriaceae. Strain MN12-7(T) was catalase-, oxidase- and cellulase-positive and lacked gelatinase, urease, lipase and pectinase. The predominant cellular fatty acids were summed feature 3 (comprising C16 : 1ω7c and/or C16 : 1ω6c), iso-C15 : 0 and C15 : 1ω6c. The major respiratory quinone of strain MN12-7(T) was MK-7, and the major polar lipid was phosphatidylethanolamine in addition to phosphatidylserine, seven unidentified lipids and six unidentified aminolipids. The DNA G+C content of strain MN12-7(T) was 38 mol%. Strain MN12-7(T) formed a separate lineage in a cluster containing 'Candidatus comitans', with which it shared 92.3 % 16S rRNA gene sequence similarity. Based on the phenotypic characteristics and phylogenetic inference, strain MN12-7(T) is proposed as a representative of a novel species in a new genus, Arcticibacter svalbardensis gen. nov., sp. nov. The type strain of the type species is MN12-7(T) ( = KCTC 32015(T) = CIP 110422(T)).

Diversity of chemotactic heterotrophic bacteria associated with arctic cyanobacteria.

The abundance and diversity of chemotactic heterotrophic bacteria associated with Arctic cyanobacteria was determined. The viable numbers ranged between 10(4) and 10(6) cell g(-1) cyanobacterial biomass. A total of 112 morphotypes, representing 22 phylotypes based on their 16S rRNA sequence similarity were isolated from the samples. All the phylotypes were Gram-negative with affiliation to the proteobacterial and bacteroidetes divisions. Among the 22 phylotypes, 14 were chemotactic to glucose. Majority of the phylotypes were psychrotolerant showing growth up to 30 °C. Representatives of Alphaproteobacteria, the genus Flavobacterium and the gammaproteobacterial Alcanivorax sp, were psychrophilic with growth at or below 18 °C. A significant percentage of phylotypes were pigmented (~68 %), rich in unsaturated membrane fatty acids and tolerated pH values and NaCl concentrations between 5.0-8.0 and 0.15-1.0 M, respectively. The percentages of phylotypes producing extracellular cold-active enzymes at 4 °C were amylase (18.18 %), lipase and urease (45.45 %), caseinase (59.09 %) and gelatinase (31.8 %).

Antagonistic interaction networks among bacteria from a cold soil environment.

Microbial antagonism in an Arctic soil habitat was demonstrated by assessing the inhibitory interactions between bacterial isolates from the same location. Of 139 isolates obtained from five soil samples, 20 antagonists belonging to the genera, Arthrobacter, Pseudomonas and Flavobacterium were identified. Inter-genus, inter-species and inter-strain antagonism was observed between the interacting members. The extent of antagonism was temperature dependent. In some cases, antagonism was enhanced at 4 °C but suppressed at 18 °C while in some the reverse phenomenon was observed. To interpret antagonism from an ecological perspective, the interacting members were delineated according to their positional roles in a theoretical antagonistic network. When only one antimicrobial producer (P) was present, all the other members permitted grouping into either sensitive (S) or resistant (R). Composite interactive types such as PSR, PS, PR or SR could be designated only when at least two producers were present. Mapping of all possible antagonistic interaction networks based on the individual positional roles of the interactive types illustrates the existence of complex and interconnected networks among microbial communities.