A novel Gram-stain-negative, strictly aerobic, non-flagellated and rod-shaped bacterium, designated HF004, was isolated from a marine sediment sample collected from the coast of Weihai, China. The strain grew optimally at 28 °C, pH 7.5-8.0 and in the presence of 2.0-3.0 % (w/v) NaCl. Based on the 16S rRNA gene sequence analysis, strain HF004 was a member of the genus Halioglobus, appearing to be closely related to Halioglobus pacificus (96.1 %) and Halioglobus japonicus (95.6 %). The major fatty acids were summed feature 3 (i.e. C16 : 1ω7c and/or iso-C15 : 0 2-OH), C17 : 1ω8c and C18 : 1ω7c. The major polar lipids were diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylglycerol. The predominant respiratory quinone was Q-8. The DNA G+C content was 57.2 mol%. Cells of strain HF004 were rod-shaped and formed circular, mucous and beige-pigmented colonies on marine agar after incubation for 72 h at 28 °C. On the basis of phenotypic, genotypic and phylogenetic evidence, strain HF004 is presented as a novel species, for which the name Halioglobus lutimaris sp. nov. is proposed. The type strain is HF004 (=KCTC 42395=MCCC 1H00127).

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Plant nonspecific lipid transfer proteins (nsLTPs) are involved in a number of biological processes including root nodule symbiosis. However, the role of nsLTPs in legume-rhizobium symbiosis remains poorly understood, and no rhizobia proteins that interact with nsLTPs have been reported to date. In this study, we used a bacteria two-hybrid system and identified the high temperature protein G (HtpG) from Mesorhizobium huakuii that interacts with the nsLTP AsE246. The interaction between HtpG and AsE246 was confirmed by far-Western blotting and bimolecular fluorescence complementation. Our results indicated that the heat shock protein 90 (HSP90) domain of HtpG mediates the HtpG-AsE246 interaction. Immunofluorescence assay showed that HtpG was colocalized with AsE246 in infected nodule cells and symbiosome membranes. Expression of the htpG gene was relatively higher in young nodules and was highly expressed in the infection zones. Further investigation showed that htpG expression affects lipid abundance and profiles in root nodules and plays an essential role in nodule development and nitrogen fixation. Our findings provide further insights into the functional mechanisms behind the transport of symbiosome lipids via nsLTPs in root nodules.

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