Psychromicrobium silvestre gen. nov., sp. nov., an actinobacterium isolated from alpine forest soils

Psychromicrobium Xiongbiense sp. nov., an Actinobacterium Isolated from Forest Soil

A novel Gram-stain-positive, oval-shaped, and non-flagellated bacterial strain YIM S02556T was isolated from forest soil in Xiongbi Town, Shizong County, Qujing City, Yunnan Province, southwestern China. The strain exhibited high pairwise 16 S rRNA gene sequence similarity with Psychromicrobium lacuslunae (97.3%) and Psychromicrobium silvestre (96.3%). Strain YIM S02556T exhibited an average nucleotide identity (ANI) of 72.5% with P. lacuslunae IHBB 11,108T and 72.8% ANI with P. silvestre AK 20-18T. The digital DNA-DNA hybridization (dDDH) value between strain YIM S02556T and P. lacuslunae IHBB 11,108T was 20.2%, while with P. silvestre AK 20-18T, the dDDH value was 20.8%. Strain YIM S02556T exhibited optimal growth at 28 °C, pH 7.0, without NaCl. Growth occurred within 10-37 ℃, pH 5.0-8.0, and in the presence of up to 5% w/v NaCl concentration. The genome size was 3.1 Mbp with 64.2% G + C content. The predominant menaquinone was MK-8(H4). The major cellular fatty acid was anteiso-C15:0. Based on the polyphasic analysis, strain YIM S02556T (= KCTC 49,805T = CCTCC AB2020166T) represents a novel Psychromicrobium species in which the name Psychromicrobium xiongbiense sp.nov. was proposed.

Salicylate or Phthalate: The Main Intermediates in the Bacterial Degradation of Naphthalene

Polycyclic aromatic hydrocarbons (PAHs) are widely presented in the environment and pose a serious environmental threat due to their toxicity. Among PAHs, naphthalene is the simplest compound. Nevertheless, due to its high toxicity and presence in the waste of chemical and oil processing industries, naphthalene is one of the most critical pollutants. Similar to other PAHs, naphthalene is released into the environment via the incomplete combustion of organic compounds, pyrolysis, oil spills, oil processing, household waste disposal, and use of fumigants and deodorants. One of the main ways to detoxify such compounds in the natural environment is through their microbial degradation. For the first time, the pathway of naphthalene degradation was investigated in pseudomonades. The salicylate was found to be a key intermediate. For some time, this pathway was considered the main, if not the only one, in the bacterial destruction of naphthalene. However, later, data emerged which indicated that gram-positive bacteria in the overwhelming majority of cases are not capable of the formation/destruction of salicylate. The obtained data made it possible to reveal that protocatechoate, phthalate, and cinnamic acids are predominant intermediates in the destruction of naphthalene by rhodococci. Pathways of naphthalene degradation, the key enzymes, and genetic regulation are the main subjects of the present review, representing an attempt to summarize the current knowledge about the mechanism of the microbial degradation of PAHs. Modern molecular methods are also discussed in the context of the development of “omics” approaches, namely genomic, metabolomic, and proteomic, used as tools for studying the mechanisms of microbial biodegradation. Lastly, a comprehensive understanding of the mechanisms of the formation of specific ecosystems is also provided.

Psychromicrobium lacuslunae sp. nov., isolated from a high altitude lake

The novel strain IHBB 11108^T was a psychrotolerant and alkaliphilic bacterium isolated from the subsurface water of Chandra Tal Lake in the Lahaul-Spiti valley located in the Indian trans-Himalayas. Cells were Gram-stain-positive, aerobic, non-motile, catalase-positive and oxidase-negative. The strain grew at 5-37 °C (optimum 28 °C), pH 5.0-12.0 (optimum pH 7.0) and with up to 8 % NaCl (optimum 1 %). The 16S rRNA gene sequence analysis revealed the highest relatedness of strain IHBB 11108^T with Psychromicrobium silvestre DSM 102047^T (97.5 %), Arthrobacter russicus DSM 14555^T (97.4 %) and Renibacterium salmoninarum ATCC 33209^T (97.4 %). The strain contained a quinone system with 57.2 % MK-9(H2), 39.1 % MK-10(H2), 3.0 % MK-8(H2) and 0.7 % MK-7(H2). The polar lipids detected were diphosphatidylglycerol, dimannosylglyceride, phosphatidylinositol, phosphatidylglycerol, monogalactosyldiacylglycerol, one unidentified glycolipid and four unidentified lipids. The cell-wall peptidoglycan structure type was A3α l-Lys-l-Thr-l-Ala with substitution of the α-carboxyl group of d-Glu by alanine amide. Anteiso-C15 : 0, iso-C16 : 0 and anteiso-C17 : 0 were the predominant fatty acids. The genomic DNA G+C content was 59.0 mol%. The DNA-DNA relatedness of strain IHBB 11108^T was 46.7±2.2, 43.1±2.5 and 19.1±2.4 % with P. silvestre DSM 102047^T, A. russicus DSM 14555^T and R. salmoninarum ATCC 33209^T, respectively. On the basis of the results of the phenotypic, chemotaxonomic and phylogenetic analyses, IHBB 11108^T is considered to represent a novel species of the genus Psychromicrobium for which the name Psychromicrobium lacuslunae sp. nov. is proposed. The type strain is IHBB 11108^T (=MTCC 12460^T=MCC 2780^T=JCM 31143^T=KACC 19070^T).