A distinct class of GTP-binding proteins mediates chloroplast protein import in Rhodophyta.

Chloroplast protein import is mediated by translocons named TOC and TIC on the outer and inner envelope membranes, respectively. Translocon constituents are conserved among green lineages, including plants and green algae. However, it remains unclear whether Rhodophyta (red algae) share common chloroplast protein import mechanisms with the green lineages. We show that in the rhodophyte Cyanidioschyzon merolae, plastome-encoded Tic20pt localized to the chloroplast envelope and was transiently associated with preproteins during import, suggesting its conserved function as a TIC constituent. Besides plastome-encoded FtsHpt and several chaperones, a class of GTP (guanosine 5'-triphosphate)-binding proteins distinct from the Toc34/159 GTPase family associated transiently with preproteins. This class of proteins resides mainly in the cytosol and shows sequence similarities with Sey1/RHD3, required for endoplasmic reticulum membrane fusion, and with the periplastid-localized import factor PPP1, previously identified in the Apicomplexa and diatoms. These GTP-binding proteins, named plastid targeting factor for protein import 1 (PTF1) to PTF3, may act as plastid targeting factors in Rhodophyta.

Bacillus pocheonensis sp. nov., a moderately halotolerant, aerobic bacterium isolated from soil of a ginseng field.

A Gram-positive, non-motile, endospore-forming bacterial strain, designated Gsoil 420T, was isolated from soil of a ginseng field in Pocheon Province, South Korea, and was characterized, using a polyphasic approach, in order to determine its taxonomic position. The novel isolate consisted of strictly aerobic, rod-shaped cells and was able to grow in medium supplemented with up to 12% NaCl at 25 degrees C and pH 6.5-7.0. Comparative 16S rRNA gene sequence analysis showed that strain Gsoil 420T fell within the radiation of the cluster comprising Bacillus species and formed a coherent cluster with Bacillus niacini (16S rRNA gene sequence similarity, 98.6%), Bacillus bataviensis (98.6%), Bacillus soli (98.3%), Bacillus drentensis (98.0%), Bacillus novalis (98.0%), Bacillus vireti (97.9%), Bacillus foraminis (97.6%), Bacillus fumarioli (97.4%) and Bacillus jeotgali (97.0%). The levels of 16S rRNA gene sequence similarity with respect to other Bacillus species with validly published names were less than 96.8%. Strain Gsoil 420T had a genomic DNA G+C content of 44.9 mol% and the predominant respiratory quinone was MK-7. The major fatty acids were anteiso-C15:0 (33.9%), iso-C15:0 (24.5%) and iso-C14:0 (19.9%). These chemotaxonomic results supported the affiliation of strain Gsoil 420T to the genus Bacillus. However, low DNA-DNA relatedness values and distinguishing phenotypic characteristics allowed genotypic and phenotypic differentiation of strain Gsoil 420T from recognized Bacillus species. On the basis of its phenotypic properties and phylogenetic distinctiveness, strain Gsoil 420T represents a novel species of the genus Bacillus, for which the name Bacillus pocheonensis sp. nov. is proposed. The type strain is Gsoil 420T (=KCTC 13943T=DSM 18135T).