Arenicella chitinivorans sp. nov., a gammaproteobacterium isolated from the sea urchin Strongylocentrotus intermedius

Fine-scale transition to lower bacterial diversity and altered community composition precedes shell disease in laboratory-reared juvenile American lobster

The American lobster Homarus americanus supports a valuable commercial fishery in the Northeastern USA and Maritime Canada; however, stocks in the southern portion of the lobster's range have shown declines, in part due to the emergence of shell disease. Epizootic shell disease is a bacterially induced cuticular erosion that renders even mildly affected lobsters unmarketable because of their appearance, and in more severe cases can cause mortality. Despite the importance of this disease, the associated bacterial communities have not yet been fully characterized. We sampled 2 yr old, laboratory-reared lobsters that displayed signs of shell disease at the site of disease as well as at 0.5, 1, and 1.5 cm away from the site of disease to determine how the bacterial community changed over this fine spatial scale. Illumina sequencing of the 16S rRNA gene revealed a distinct bacterial community at the site of disease, with significant reductions in bacterial diversity and richness compared to more distant sampling locations. The bacterial community composition 0.5 cm from the site of disease was also altered, and there was an observable decrease in bacterial diversity and richness, even though there were no signs of disease at that location. Given the distinctiveness of the bacterial community at the site of disease and 0.5 cm from the site of disease, we refer to these communities as affected and transitionary, and suggest that these bacteria, including the previously proposed causative agent, Aquimarina 'homaria', are important for the initiation and progression of this laboratory model of shell disease.

Perspicuibacter marinus gen. nov., sp. nov., a semi-transparent bacterium isolated from surface seawater, and description of Arenicellaceae fam. nov. and Arenicellales ord. nov

A Gram-stain-negative, non-motile, mesophilic, aerobic, rod-shaped bacterium, strain 2-9(T), was isolated from surface seawater at Muroto city, Kochi prefecture, Japan. The strain was transparent on 1/5 strength marine broth plate but became easily visible when the plate was supplemented with pyruvate. Phylogenetic analyses based on the 16S rRNA gene sequence showed that the strain fell within the class Gammaproteobacteria and was most closely related to the genus Arenicella (92.7-93.0 % 16S rRNA gene sequence similarities to type strains of species of this genus) of an unclassified order within this class. The DNA G+C content of strain 2-9(T) was 41.7 mol%. The major fatty acids were C18 : 1ω7c (37.6 %), C16 : 1ω7c and/or iso-C15 : 0 2-OH (summed feature 3; 19.1 %), C18 : 0 (10.8 %), C16 : 0 (10.2 %) and an unidentified fatty acid with an equivalent chain-length value of 11.799 (9.5 %). The major polar lipids were phosphatidylglycerol, phosphatidylethanolamine and three unidentified lipids. Ubiquinone-8 (Q-8) was detected as the sole isoprenoid quinone. From these taxonomic data, it is proposed that strain 2-9(T) represents a novel species of a new genus, Perspicuibacter marinus gen. nov., sp. nov. The type strain of the type species is 2-9(T) ( = NBRC 110144(T) = KCTC 42196(T)). A new family, Arenicellaceae fam. nov. (type genus Arenicella), and order, Arenicellales ord. nov., of the class Gammaproteobacteria are proposed to accommodate the novel taxon.