RESUMEN
Three new phlegmaciod species of Thaxterogaster, T. borealicremeolinus, T. rufopurpureus, and T. sinopurpurascens spp. nov., from subtropical China were described based on their morphological characteristics and molecular data. Thaxterogaster borealicremeolinus belongs to the sect. Cremeolinae and differs from the other species in this section in its larger basidiospores and its habitat in the Northern Hemisphere associated with Quercus sp. trees. Thaxterogaster rufopurpureus and T. sinopurpurascens belong to sect. Purpurascentes, in which T. rufopurpureus is characterized by a pileus with a reddish-brown coloration when mature and a clavate stipe, while T. sinopurpurascens is characterized by a violet basidiomata, except for a greyish orange to brown pileus, the distinctly marginate bulb of its stipe, and its distribution in subtropical China. The phylogenetic analyses were performed based on nrITS, and detailed descriptions of the new species are provided herein.
RESUMEN
From exoR'-11 which could complement two Exo(-) mutants of R. huakuii 107: NA03 and NA10, a 2.0kb BglI fragment was subcloned in pRK415. The resulted plasmid pJB-H701 could restore the Exo(-) phenotype of NA03 and NA10. The complete nucleotide sequence of the fragment was determined, which contains the structural genes of a glucosyl-transferase, as well as the 5'- and 3'- flanking regions. An open reading frame of 984 base pairs was identified as R. huakuii exoA gene. The MW of ExoA, as deduced from the nucleotide sequence, was estimated as 35 kD. Comparison of the nucleotide sequences revealed a high similarity between exoA genes of R. huakuii and R. meliloti. The deduced amino acid sequence of R. huakuii ExoA also showed a high similarity with that of R. meliloti ExoA. Furthermore, the exoA-lacZ transcription fusion gene was constructed and the expression of exoA-lacZ was analyzed.
RESUMEN
We have subcloned two plasmids, pWS-6BP1 and pWS-6BP2, from the 8.5 kb DNA fragment of plasmid pJB22-B6. The plasmid of pWS-6BP1, with a 5.8 kb DNA fragment, can complement the exopolysaccharide-deficient mutant NA06 and NA12 of Rhizobium huakuii strain 107, but the plasmid pWS-6BP2, with a 2.6 kb DNA fragment can only complement NA12. The effective nodules formed by the wild type strain 107 (Rh107) contain lots of bacteriods; the ineffective nodules formed by the mutant NA06 and NA12 contain few bacteroids. Although the nodule formed by Exo(+) transconjugants are ineffective, the bacteria can be successfully released into the cells and form lots of bacteroids. The Rh107 produces acidic exopolysaccharides (EPS) of high molecular weight (HMW) in large amount with only small amount of low molecular weight (LMW) forms. EPS secreted by mutants NA06 and NA12 are just the other way round with LMW in higher amount than HMW ones. They also produce an EPS with molecular weight in between. The EPS secreted by the Exo(+) transconjugants is more like the EPS of Rh107 than that of mutants, although their component and structure are still different from that of Rh107.