Publications

4053

SummaryTwo phylogenetically distinct marine strains producing transparent exopolymers (TEP), designated HTCC2155T and HTCC2160, were cultivated from Oregon coast seawater by dilution to extinction in a high throughput culturing format. When cultured in low‐nutrient seawater media, these strains copiously produced Alcian Blue‐stainable viscous TEP. Growing cells were attached to each other by the TEP in a three dimensional network. Polymerase chain reaction employing 16S rDNA primers specific for the novel isolates indicated that they are indigenous to the water column of the Atlantic and Pacific oceans. The abundance of the isolates as determined by 16S rRNA dot blots, however, indicated that they are less than 1% of the total bacterial community. In phylogenetic analyses, the strains consistently formed a new phylum‐level lineage within the domain Bacteria, together with members of the candidate phylum VadinBE97, which consists of Victivallis, the first cultured genus in the candidate phylum, and 16S rRNA gene clones from DNA extracted from marine or anaerobic terrestrial habitats. Five putative subgroups were delineated within this phylum‐level lineage, including a marine group and an anaerobic group. The isolates are Gram negative, strictly aerobic, chemoheterotrophic, and facultatively oligotrophic sphere‐shaped bacteria. The DNA G+C content of strain HTCC2155T was 48.3 mol% and the genome size was 2.9 mb. It is proposed from these observations that the strains be placed into a new genus and a new species named Lentisphaera araneosa (type strain HTCC2155T = ATCC BAA‐859T = KCTC 12141T) gen. nov., sp. nov., the cultured marine representative of the Lentisphaerae phyl. nov., and the phylum be divided into two novel orders named the Lentisphaerales ord. nov. and the Victivallales ord. nov.

Previously, analysis of 16S rDNA sequences placed a newly discovered lineage of bacterial symbionts of arthropods in the ‘Bacteroidetes’. This symbiont lineage is associated with a number of diverse host reproductive manipulations, including induction of parthenogenesis in severalEncarsiaparasitoid wasps (Hymenoptera: Aphelinidae). In this study, electron microscopy and phylogenetic analysis of the 16S rRNA andgyrBgenes of symbionts fromEncarsia hispidaandEncarsia pergandiellaare used to describe and further characterize these bacteria. Phylogenetic analyses based on these two genes showed that theEncarsiasymbionts are allied with theCytophaga aurantiacalineage within the ‘Bacteroidetes’, with their closest described relative being the acanthamoeba symbiont ‘CandidatusAmoebophilus asiaticus’. TheEncarsiasymbionts share 97 % 16S rDNA sequence similarity withBrevipalpusmite andIxodestick symbionts and 88 % sequence similarity with ‘CandidatusA. asiaticus’. Electron microscopy revealed that many of the bacteria found in the ovaries of the twoEncarsiaspecies contained a regular, brush-like array of microfilament-like structures that appear to be characteristic of the symbiont. Finally, the role of this bacterium in parthenogenesis induction inE. hispidawas confirmed. Based on phylogenetic analyses and electron microscopy, classification of the symbionts fromEncarsiaas ‘CandidatusCardinium hertigii’ is proposed.