Incompatibility behavior of a symbiotic plasmid pMH7653Rb in Mesorhizobium huakuii 7653R.

Mesorhizobium huakuii strain 7653R harbored two indigenous plasmids named pMH7653Ra and pMH7653Rb. The larger plasmid pMH7653Rb (symbiotic plasmid) was transferred to M. huakuii HN308SR harboring three plasmids: pMHHN308a, pMHHN308b and pMHHN308c, and HN3015SR harboring three plasmids: pMHHN3015a, pMHHN3015b and pMHHN3015c by tri-parent mating.

BacA is indispensable for successful Mesorhizobium-Astragalus symbiosis.

A homologue of Sinorhizobium meliloti bacA was isolated from Mesorhizobium huakuii 7653R, which is capable of fixing atmospheric nitrogen in symbiotic association with leguminous Astragalus sinicus (Chinese milk vetch). Inactivation of the bacA gene abolished the ability of M. huakuii 7653R to establish a successful symbiosis with its host plant.

Genetic diversity of root-nodulating bacteria isolated from pea (Pisum sativum) in subtropical regions of China.

Diversity of 42 isolates from effective nodules of Pisum sativum in different geographical regions of China were studied using 16S rRNA gene RFLP patterns, 16S rRNA sequencing, 16S-23S rRNA intergenic spacer (IGS) region RFLP patterns and G-C rich random amplified polymorphic DNA (RAPD). The isolates were distributed in two groups on the basis of their 16S rRNA gene RFLP patterns. The 16S rRNA gene sequences of strains from 16S rRNA gene RFLP patterns group I were very closely related (identities higher than 99.

A nodule-specific plant cysteine proteinase, AsNODF32, is involved in nodule senescence and nitrogen fixation activity of the green manure legume Astragalus sinicus.

Asnodf32, encoding a nodule-specific cysteine proteinase in Astragalus sinicus, is probably involved in nodule senescence. To obtain direct evidence of its role in nodule senescence, Agrobacterium rhizogenes-mediated RNA interference was applied to A. sinicus hairy roots.

Cloning and identification of lpsH, a novel gene playing a fundamental role in symbiotic nitrogen fixation of Mesorhizobium huakuii.

Mesorhizobium huakuii 7653R forms a symbiotic relationship with Astragalus sinicus to produce nitrogen-fixing root nodules under nitrogen-limiting conditions. By screening its transposon-inserted mutant library, a mutation in the lpsH gene was found to form pseudonodules on A. sinicus.

The symbiosis phenotype and expression patterns of five nodule-specific genes of Astragalus sinicus under ammonium and salt stress conditions.

In previous works, we isolated 14 nodule-specific or nodule-enhanced genes from Astragalus sinicus by suppressive subtractive hybridization. In this study, we have further identified the expression patterns of five nodule-specific genes of A. sinicus under salt and ammonium stress.

[Studies on genetic diversity and phylogeny of slow-growing rhizobia isolated from Vigna radiata at main ecotypes of China].

Studies on genetic diversity and phylogeny of slow-growing rhizobia isolated from Vigna radiata at main ecotypes of China were conducted by using 16S rRNA gene PCR-RFLP, 16S rRNA gene sequencing and 16S-23S rRNA IGS PCR-RFLP assays. Results of 16S rRNA gene PCR RFLP analysis reveal that all the strains tested are clustered into three groups at the similarity of 76%. Group I contains 13 slow-growing rhizobia tested including LYG1; Group II consists of 21 strains tested and the type strains of B.

A novel nodule-enhanced gene encoding a putative universal stress protein from Astragalus sinicus.

A nodule-enhanced gene, AsD243, was identified from infected roots of Astragalus sinicus using suppressive subtractive hybridization (SSH). It encodes a 20-kD protein related to the bacterial universal stress protein family (Usp). Sequence analysis showed that AsD243 is highly similar to the bacterial MJ0577-type of ATP-binding Usp proteins, which have been proposed to function as a molecular switch.

Thirteen nodule-specific or nodule-enhanced genes encoding products homologous to cysteine cluster proteins or plant lipid transfer proteins are identified in Astragalus sinicus L. by suppressive subtractive hybridization.

Thirteen nodule-specific or nodule-enhanced genes have been revealed by suppressive subtractive hybridization (SSH) with two mRNA populations of infected and uninfected control roots of Astragalus sinicus. Eleven of them encode small polypeptides showing homology to cysteine cluster proteins (CCPs) that contain a putative signal peptide and conserved cysteine residues. Among these CCP-like genes, AsG257 codes for a homologue of the defensin 2 family and AsD255 contains a scorpion toxin-like domain at the C-terminus.

[Genetic diversity and phylogeny of soybean bradyrhizobia isolated from south and north region of China].

Studies on genetic diversity and phylogeny of soybean bradyrhizobia isolated from south and north region of China were investigated through 16S rRNA gene PCR RFLP, 16S rRNA gene sequencing and 16S-23S rRNA IGS PCR RFLP assays. Results of 16S rRNA gene PCR RFLP and 16S rRNA gene sequencing analysis reveal that strains tested are ascribed into Bradyrhizobium japonicum and B. elkanii species.

Apparent incompatibility of plasmid pSfrYC4b of Sinorhizobium fredii with two different plasmids in another strain.

Sinorhizobium fredii YC4B is a spontaneous mutant derivative of strain YC4 that is unable to nodulate soybeans. The second-largest plasmid of strain YC4B, termed pSfrYC4b (810 kb), was transferred to S. fredii HN01SR, a strain which contains three large indigenous plasmids (pSfrHN01a, pSfrHN01b and pSfrHN01c).

[Effects of bkdAB interruption on avermectin biosynthesis].

In this study, Streptomyces avermitilis Bjbm0006 which produces four avermectin B components was used as an original test strain. A replacement plasmid containing a gene cluster bkdAB (branched-chain alpha-keto acid dehydrogenase gene) involved in the biosynthesis of avermectin B in S. avermitilis Bjbm0006 was constructed by means of PCR technique and then named as pHJ5821 (pHZ1358::bkdAB&erm).

Effect of nisin on the growth of Staphylococcus aureus determined by a microcalorimetric method.

A novel microcalorimetric technique based on the bacterial heat output was applied to evaluate the biological effect of nisin on the growth of Staphylococcus aureus. The thermogenic curves of S. aureus in the presence of nisin were studied by an LKB-2277 Thermal Activity Monitor.

[Effect of Sinorhizobium fredii YC4 symbiotic plasmid amplification on nod factors and symbiotic N-fixation].

Sinorhizobium fredii YC4 can form nitrogen-fixing nodules on soybean (Glycine max) and wild soybean (G. soja). It can produce unique lipochitooligosaccharide nod factors (LCOs), in comparison with the other four strains of S.

[Root colonization and nodulation of Sinorhizobium fredii HN01DL in Glycine max rhizosphere].

Rhizobox-soil microcosms studies on the colonization, dispersal and nodulation of Sinorhizobium fredii HN01DL marked with luxAB gene in Glycine max rhizosphere showed that the colonization dynamics and the density of HN01DL in non-sterilized rhizobox-soil microcosms were different from those in sterilized rhizobox-soil microcosms. The colonization density of the former reached the maximum (8.65 log cfu.

[Genetic diversity and phylogeny of rhizobia isolated from peanut (Arachis hypogaea)].

Forty three rhizobium strains isolated from peanut (Arachis hypogaea) and 15 reference strains from other genus and species were analyzed by the method of 16S rRNA RFLP, 16S rRNA sequencing and 16S-23S IGS PCR RFLP. The results of the 16S rRNA RFLP shown that 43 strains tested were all ascribed to the genus of Bradyrhizobium phylogenetically. Strains tested were adjacent to the B.

[A study of the effects on the symbiotic nitrogen fixation of Sinorhizobium fredii with the introduction of dctABD and nifA genes].

A recombinant plasmid pHN307 containing C4-dicarboxylic acid transport genes (dctABD) from Sinorhizobium meliloti, nifA genes from Klebsiella pneumoniae and reporter genes luxAB from pDB30 was constructed by using pTR102 as the vector. The pHN307 was then introduced into the S. fredii HN01, YC4 and GR3 by tri-parental mating, and the stability of pHN307 in the transconjugants under free-living and symbiotic condition was also investigated.