Taxonomic studies on methylotrophic bacteria by 5S ribosomal RNA sequencing

Nucleotide sequences of 5S ribosomal RNA (rRNA) isolated from 19 strains of Gram-negative methylotrophic bacteria were determined. Comparison of these sequences allowed construction of a tentative phylogenetic tree and showed that the bacteria analysed belong to the Proteobacteria and fell into several clusters, including obligate methanotrophs, obligate methylotrophs and several groups of facultative methylotrophs. Taxonomic relations between methylotrophic and non-methylotrophic bacteria are discussed, and the polyphyletic nature of methylotrophy as a taxonomic feature is highlighted.     

Characterization of catalase-negative mutants of methylotrophic yeastHansenula polymorpha

Three recently isolated catalase-negative mutants ofHansenula polymorpha lost the ability to grow on methanol but grew in media containing glucose, ethanol or glycerol. Their incubation in a medium with methanol resulted in an accumulation of hydrogen peroxide and cell death. During growth of a catalase-negative mutant in chemostat on a mixture of methanol and glucose, neither H₂O₂ accumulation nor cell death were observed up to the molar ratio of 10:1 of the two substrates. Cytochrome-c peroxidase and NADH-peroxidase activities were detected in the cells. In methylotrophic yeasts, catalase seems to be an enzyme characteristic of the metabolism of methanol but not needed for the metabolism of multicarbon substrates. The hydrogen peroxide produced during growth of the mutants on mixed substrates is detoxified by cytochrome-c peroxidase and other peroxidases. Translated by Č. Novotny     

The influence of colonizing methylobacteria on morphogenesis and resistance of sugar beet and white cabbage plants to <Emphasis Type="Italic">Erwinia carotovora</Emphasis>

The influence of colonization of sugar beet (Beta vulgaris var. saccharifera (Alef) Krass) and white cabbage (Brassica oleracea var. capitata L.) plants by methylotrophic bacteria Methylovorus mays on the growth, rooting, and plant resistance to phytopathogen bacteria Erwinia carotovora was investigated. The colonization by methylobacteria led to their steady association with the plants which had increased growth speed, root formation and photosynthetic activity. The colonized plants had increased resistance to Erwinia carotovora phytopathogen and were better adapted to greenhouse conditions. The obtained results showed the perspectives for the practical implementation of methylobacteria in the ecologically clean microbiology substances used as the plant growth stimulators and for the plant protection from pathogens.     

Reclassification of Methylarcula marina Doronina et al. 2000 as Paracoccus methylarcula nom. nov.

Microbiology - Phylogenetic analysis of the 16S rRNA gene sequences showed that the type species of the genus Methylarcula, Methylarculamarina h1T was closely related to Paracoccus saliphilus DSM...     

Halophilic and halotolerant aerobic methylobacteria from the technogenic Solikamsk biotopes

Seven strains of moderately halophilic and halotolerant aerobic methylobacteria from the technogenic Solikamsk biotopes (Perm krai, Russia) were isolated in pure cultures and characterized. The isolates were represented by gram-negative and gram-positive (strain 2395B) cells. All the cells were shown to multiply by binary fission without formation of spores or prosthecae. All isolates except strain 2395B were able to oxidize methanol by a classical methanol dehydrogenase. The ribulose monophosphate (RMP) (strain LS), serine (strains S12, S3, 2395A), or ribulose bisphosphate (strains SK15 and S3270) pathways of C₁-assimilation were used. In strain 2395B, the key enzymes of the RMP and serine metabolic pathways were determined. Using polyphasic taxonomy, three strains were identified as representatives of the known species: Arthrobacter protophormiae 2395B, Methylophaga thalassica LS, and Ancylobacter rudongensis S3270. Three more strains were identified as members of new species: Methylopila oligotropha sp. nov. (strain 2395AT; VKM B-2788^T = CCUG 63805^T), Ancylobacter defluvii sp. nov. (strain SK15^T; VKM B-2789^T = CCUG 63806^T), and Paracoccus communis sp. nov. (strain S3^T; VKM B-2787^T = CCUG 63804^T). According to the results of 16S rRNA gene sequencing, the obligately methylotrophic strain S12 had less than 94% similarity with the known genera of the Proteobacteria and was probably a representative of a novel genus.     

Unravelling mitochondrial retrograde regulation in the abiotic stress induction of rice ALTERNATIVE OXIDASE 1 genes

Mitochondrial retrograde regulation (MRR) is the transduction of mitochondrial signals to mediate nuclear gene expression. It is not clear whether MRR is a common regulation mechanism in plant abiotic stress response. In this study, we analysed the early abiotic stress response of the rice OsAOX1 genes, and the induction of OsAOX1a and OsAOX1b (OsAOX1a/b) was selected as a working model for the stress‐induced MRR studies. We found that the induction mediated by the superoxide ion (O_2·^‐)‐generating chemical methyl viologen was stronger than that of hydrogen peroxide (H₂O₂). The addition of reactive oxygen species (ROS) scavengers demonstrated that the stress induction was reduced by eliminating O_2·^‐. Furthermore, the stress induction did not rely on chloroplast‐ or cytosol‐derived O_2·^‐. Next, we generated transgenic plants overexpressing the superoxide dismutase (SOD) gene at different subcellular locations. The results suggest that only the mitochondrial SOD, OsMSD, attenuated the stress induction of OsAOX1a/b specifically. Therefore, our findings demonstrate that abiotic stress initiates the MRR on OsAOX1a/b and that mitochondrial O_2·^– is involved in the process.     

新生儿肺炎的临床表现及x线特征的探讨

目的：探讨新生儿肺炎（neonatal pneumonia,NP）的临床表现及x线特征,以提高对NP的临床认识。方法：选择2011年6月至2012年10月在我院确诊为NP的新生儿73例,均经x线检查,回顾性分析患儿的临床资料,总结并分析患儿的临床表现及x线特征。结果：NP患儿的临床症状主要表现为呼吸急促、发绀、咳嗽、吐沫、呛奶和三凹征,部分患儿体温正常;NP的x线影像表现具有多样性,以不同程度的支气管肺炎多见,主要表现为肺纹理增多增密,局部肺野透光度降低或透光度增强。结论：NP患儿的临床症状以呼吸急促、发绀、咳嗽、吐沫、呛奶和三凹征为主,x线检查可为NP的早期诊断提供重要的临床信息,临床医师应根据NP患儿的x线影像的多样性,密切结合患儿的临床症状,做出综合分析。     

异丙酚和氯胺酮对大鼠离体缺血再灌注损伤心肌脂质过氧化的影响

目的：比较异丙酚和氯胺酮对大鼠离体缺血再灌注损伤心肌脂质过氧化的影响。方法：成年Wistar大鼠18只,雌雄不拘。体重240-300g,随机分为3组（T1=6）：心肌缺血再灌注损伤组（I／R组）,异丙酚组（P组）,氯胺酮组（K组）。采用Langendorff灌装置建立离体心脏缺血再灌注模型,将心脏连接至Langendorff逆灌装置,3组均以K-H液平衡灌注10min后,再分别以K．H液、含30μmol/L。异丙酚的K-H液、含10μmol-L-1氯胺酮的K-H液灌注10min,然后全心停灌25min,再分别以停灌前相同的灌注液恢复灌注30min。留取冠脉流出液测定总LDH活性;灌注末取左室心肌组织置于2．5％的戊二醛固定,观察心肌的超微结构;心尖部心肌组织留待检测8-异前列腺素和SOD活性。结果：与I／R组比较,P组8-异前列腺素含量降低,SOD活性升高,LDH活性降低（P〈0．05）;K组8-异前列腺素含量,SOD及LDH活性均无统计学意义（P〉0．05）;与P组比较,K组8-异前列腺素含量升高,SOD及LDH活性降低（P〈0．05）;P组心肌超微结构损伤较m组和K组也明显改善。结论：异丙酚可显著减轻心肌缺血再灌注损伤大鼠的脂质过氧化和心肌缺血再灌注损伤,而氯胺酮没有抗心肌缺血再灌注损伤心肌脂质过氧化的作用。