April 21, 2020  |  

Paenibacillus albus sp. nov., a UV radiation-resistant bacterium isolated from soil in Korea.

A novel Gram-stain-positive, motile, white color and endospore-forming bacterium, designated 18JY67-1T, was isolated from soil in Jeju Island, Korea. The strain grow at 15-42 °C (optimum 30 °C) in R2A medium at pH (6.0-9.5) (optimum 7.5). Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain 18JY67-1T formed a distinct lineage within the family Paenibacillaceae (order Bacillales, class Bacilli), and was closely related to Paenibacillus rhizoryzae (KP675984; 96.9% 16S rRNA gene sequence similarity). The major cellular fatty acids of the strain 18JY67-1T were C16:0 and anteiso-C15:0. The predominant respiratory quinones were MK-7. The major polar lipid was identified as diphosphatidylglycerol. On the basis of phenotypic, chemotaxonomic and genotypic properties clearly indicated that isolate 18JY67-1T represents a novel species within the genus Paenibacillus, for which the name Paenibacillus flavus sp. nov. is proposed. The type strain of Paenibacillus flavus is 18JY67-1T (=?KCTC 33959T =?JCM 33184T).


April 21, 2020  |  

Decreased biofilm formation ability of Acinetobacter baumannii after spaceflight on China’s Shenzhou 11 spacecraft.

China has prepared for construction of a space station by the early 2020s. The mission will require astronauts to stay on the space station for at least 180 days. Microbes isolated from the International Space Station (ISS) have shown profound resistance to clinical antibiotics and environmental stresses. Previous studies have demonstrated that the space environment could affect microbial survival, growth, virulence, biofilms, metabolism, as well as their antibiotic-resistant phenotypes. Furthermore, several studies have reported that astronauts experience a decline in their immunity during long-duration spaceflights. Monitoring microbiomes in the ISS or the spacecraft will be beneficial for the prevention of infection among the astronauts during spaceflight. The development of a manned space program worldwide not only provides an opportunity to investigate the impact of this extreme environment on opportunistic pathogenic microbes, but also offers a unique platform to detect mutations in pathogenic bacteria. Various microorganisms have been carried on a spacecraft for academic purposes. Acinetobacter baumannii is a common multidrug-resistant bacterium often prevalent in hospitals. Variations in the ability to cope with environmental hazards increase the chances of microbial survival. Our study aimed to compare phenotypic variations and analyze genomic and transcriptomic variations in A. baumannii among three different groups: SS1 (33 days on the Shenzhou 11 spacecraft), GS1 (ground control), and Aba (reference strain). Consequently, the biofilm formation ability of the SS1 strain decreased after 33 days of spaceflight. Furthermore, high-throughput sequencing revealed that some differentially expressed genes were downregulated in the SS1 strain compared with those in the GS1 strain. In conclusion, this present study provides insights into the environmental adaptation of A. baumannii and might be useful for understanding changes in the opportunistic pathogenic microbes on our spacecraft and on China’s future ISS. © 2018 The Authors. MicrobiologyOpen published by John Wiley & Sons Ltd.


April 21, 2020  |  

Whole-genome analysis of the colonization-resistant bacterium Phytobacter sp. SCO41T isolated from Bacillus nematocida B16-fed adult Caenorhabditis elegans.

Colonization resistance is an important attribute for bacterial interactions with hosts, but the mechanism is still not completely clear. In this study, we found that Phytobacter sp. SCO41T can effectively inhibit the in vivo colonization of Bacillus nematocida B16 in Caenorhabditis elegans, and we revealed the colonization resistance mechanism. Three strains of colonization-resistant bacteria, SCO41T, BX15, and BC7, were isolated from the intestines of the free-living nematode C. elegans derived from rotten fruit and soil. The primary characteristics and genome map of one of the three isolates was investigated to explore the underlying mechanism of colonization resistance in C. elegans. In addition, we performed exogenous iron supplementation and gene cluster knockout experiments to validate the sequencing results. The results showed that relationship was close among the three strains, which was identified as belonging to the genus Phytobacter. The type strain is SCO41T (=?CICC 24103T?=?KCTC 52362T). Whole genome analysis showed that csgA, csgB, csgC, csgE, csgF, and csgG were involved in the curli adhesive process and that fepA, fepB, fepC, fepD, and fepG played important roles in SCO41T against the colonization of B. nematocida B16 in C. elegans by competing for iron. Exogenous iron supplementation showed that exogenous iron can increase the colonization of B. nematocida B16, which was additionally confirmed by a deletion mutant strain. The csg gene family contributes to the colonization of SCO41T in C. elegans. Curli potentially contribute to the colonization of SCO41T in C. elegans, and enterobactin has a key role in SCO41T to resist the colonization of B. nematocida B16 by competing for iron.


April 21, 2020  |  

Complete genome sequence of Raoultella sp. strain X13, a promising cell factory for the synthesis of CdS quantum dots.

A novel cadmium-resistant bacterium, Raoultella sp. strain X13, recently isolated from heavy metal-contaminated soil, and this strain can synthesize CdS quantum dots using cadmium nitrate [Cd(NO4)2] and l-cysteine. Biomineralization of CdS by strain X13 can efficiently remove cadmium from aqueous solution. To illuminate the molecular mechanisms for the biosynthesis of CdS nanoparticle, the complete genome of Raoultella sp. strain X13 was sequenced. The whole genome sequence comprises a circular chromosome and a circular plasmid. Cysteine desulfhydrase smCSE has been previously found to be associated with the synthesis of CdS quantum dots. Bioinformatics analysis indicated that the genome of Raoultella sp. strain X13 encodes five putative cysteine desulfhydrases and all of them are located in the chromosome. The genome information may help us to determine the molecular mechanisms of the synthesis of CdS quantum dots and potentially enable us to engineer this microorganism for applications in biotechnology.


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