Marine Myxobacteria as a Source of Antibiotics—Comparison of Physiology, Polyketide-Type Genes and Antibiotic Production of Three New Isolates of Enhygromyxa salina

Three myxobacterial strains, designated SWB004, SWB005 and SWB006, were obtained from beach sand samples from the Pacific Ocean and the North Sea. The strains were cultivated in salt water containing media and subjected to studies to determine their taxonomic status, the presence of genes for the biosynthesis of polyketides and antibiotic production. 16S rDNA sequence analysis revealed the type strain Enhygromyxa salina SHK-1T as their closest homolog, displaying between 98% (SWB005) and 99% (SWB004 and SWB006) sequence similarity. All isolates were rod-shaped cells showing gliding motility and fruiting body formation as is known for myxobacteria. They required NaCl for growth, with an optimum concentration of around 2% [w/v]. The G + C-content of genomic DNA ranged from 63.0 to 67.3 mol%. Further, the strains were analyzed for their potential to produce polyketide-type structures. PCR amplified ketosynthase-like gene fragments from all three isolates enhances the assumption that these bacteria produce polyketides. SWB005 was shown to produce metabolites with prominent antibacterial activity, including activity towards methicillin resistant Staphylococcus aureus (MRSA) and Staphylococcus epidermidis (MRSE)

Corynebacterium marinum sp. nov. isolated from coastal sediment

A taxonomic study was performed on strain D7015T, which was isolated from coastal sediment close to a coal-fired power station in Qingdao, China. Strain D7015T comprised Gram-positive, non-motile diphtheroid rods, which grew in the presence of 0-8% (w/v) NaCl and at 4-37°C, with optimum growth at 1% (w/v) NaCl and 30-32°C. The G+C content was 65.0 mol%. The major fatty acids were C18:1ω9c (56.18%), C16:0 (38.02%), C16:1ω7c (4.45%), C18:0 (1.0%) and C14:0 (0.35%). On the basis of the morphological, physiological and phylogenetic characteristics, strain D7015T was classified in the genus Corynebacterium. It exhibited a 16S rRNA gene sequence similarity of 95.9% and a DNA:DNA relatedness value of 20.4% with Corynebacterium halotolerans DSM 44683T. Strain D7015T was sufficiently different from hitherto described Corynebacterium species to be considered as a novel species. The name Corynebacterium marinum sp. nov. is proposed, with strain D7015T (=CGMCC 1.6998T =NRRL B-24779T) as the type strain

Utilizing concrete pillars as an environmental mining practice in underground mines

Ground control is an integral element of mine design and worker safety. The use of concrete pillars for underground mines is of paramount importance to maintaining the economic and operational security of structures. This paper deals with the use of fiber-reinforced concrete (FRC) as pillars via laboratory and field tests. The strength performance of prepared concrete reinforced with glass, polypropylene and polyacrylonitrile fibers was researched by a mechanical press and a computed tomography (CT) tool. Samples were tested for fiber volume fractions of 0, 0.4, 0.8 and 1.2 wt%, respectively. Results have indicated that, with the addition of fibers, the strength was improved first due to a bridging effect and then decreased due to a pull-out effect. Compared to the reference sample, the absorbed energy prevents FRC from deterioration by mechanisms of matrix cracking, fiber-matrix interface debonding and fiber rupture. The peak strains of FRC linearly rise with increasing fiber. The gray value distribution curves have also good correspondence with 2D CT pore and crack distributions, which reveal that gray value processing could depict the structural behavior of concretes reinforced with or without fiber. Theoretical analyses show that the pillar remains stable for sustainable mining. Besides, the location and size of FRC pillars are suitable for numerical calculations of the trial stope. The findings of this study can offer a key reference for the orebody pillar recovery in underground mines. © 2020 Elsevier LtdLNM202009 National Natural Science Foundation of China: 51974012, 51804017 Fundamental Research Funds for the Central UniversitiesThis work was financially supported by the National Natural Science Foundation of China (grant numbers: 51804017 and 51974012 ), the Open Fund of State Key Laboratory of Nonlinear Mechanics (grant number: LNM202009 ) and Fundamental Research Funds for the Central Universities (Grant No. FRF-TP-20-001A2 and FRF-BD-19-005A )

An Unusual Diterpene—Enhygromic Acid and Deoxyenhygrolides from a Marine Myxobacterium, Enhygromyxa sp.

Three new compounds, enhygromic acid (1) and deoxyenhygrolides A (2) and B (3), were isolated from a marine myxobacterium, Enhygromyxa sp. Compound 1 was found to be an acrylic acid derivative with a rare polycyclic carbon skeleton, decahydroacenaphthylene, by spectroscopic analyses. Compounds 2 and 3 were deoxy analogs of the known γ-alkylidenebutenolides, enhygrolides. Compound 1 exhibited cytotoxicity against B16 melanoma cells and anti-bacterial activity against Bacillus subtilis, and enhanced the NGF-induced neurite outgrowth of PC12 cells

Isolation and Biosynthetic Analysis of Haliamide, a New PKS-NRPS Hybrid Metabolite from the Marine Myxobacterium Haliangium ochraceum

Myxobacteria of marine origin are rare and hard-to-culture microorganisms, but they genetically harbor high potential to produce novel antibiotics. An extensive investigation on the secondary metabolome of the unique marine myxobacterium Haliangium ochraceum SMP-2 led to the isolation of a new polyketide-nonribosomal peptide hybrid product, haliamide (1). Its structure was elucidated by spectroscopic analyses including NMR and HR-MS. Haliamide (1) showed cytotoxicity against HeLa-S3 cells with IC50 of 12 μM. Feeding experiments were performed to identify the biosynthetic building blocks of 1, revealing one benzoate, one alanine, two propionates, one acetate and one acetate-derived terminal methylene. The biosynthetic gene cluster of haliamide (hla, 21.7 kbp) was characterized through the genome mining of the producer, allowing us to establish a model for the haliamide biosynthesis. The sulfotransferase (ST)-thioesterase (TE) domains encoded in hlaB appears to be responsible for the terminal alkene formation via decarboxylation

Weed biological control in the Greater Mekong Subregion: status and opportunities for the future

Twenty biological control agents targeting nine weed species have been introduced into the six countries of the Greater Mekong Subregion. Thirteen of these agents have established and another nine have arrived unintentionally. These agents are having some impact on their target weeds. However, another 38 weeds occurring in the region have been targeted for biological control elsewhere presenting a tremendous opportunity to expand weed biological control in the region and reduce the dependency on herbicides while increasing productivity. Highly effective biological control agents are available for introduction and could assist with the management of the region's most important weeds, such as water lettuce, salvinia, Siam weed and mikania. There is also scope to increase the capacity and training in biological control to develop effective weed control and management

Strength development and microstructure characteristics of artificial concrete pillar considering fiber type and content effects

Yilmaz, Erol/0000-0001-8332-8471;WOS: 000540841400027The artificial concrete pillar (ACP) replacement technique is a safe and reliable method to safely mine orebody pillar in room and pillar mining. in contrast to traditional ore pillar, artificial pillar has recently received significant attention due to its applicability, stability and cost benefits. This study deals the influence of fiber type and content on uniaxial compressive strength (UCS) and microstructure characteristics of fiber-reinforced concrete (FRC) considered as an effective artificial pillar. A total of 3 non-FRC (NFRC) and 27 FRC samples reinforced with glass, polypropylene (PP), and polyacrylonitrile (PAN) fibers at a content of 0 wt%, 0.4 wt%, 0.8 wt% and 1.2 wt% were manufactured for examining their strength properties. After UCS testing, some microstructure tests including computed tomography scan and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy were done to better explore the morphology of FRC. Results illustrate that: (1) the UCS values of all FRC samples first increase and then decrease with increasing fiber content. the UCS increment ratio in FRC steadily decreases as the fiber content increases. (2) PP fiber was more effective than both glass and PAN fibers in increasing peak strain and strength performance. This was mainly because of an improved bonding quality within the matrix which allows to decrease the water absorption of FRC. Overall, the peak strain increases linearly with increasing fiber content. Finally, the findings of this study can offer a substantial reference in design and application of FRC to be used as artificial pillar in underground mines. (C) 2020 Elsevier Ltd. All rights reserved.National Natural Science Foundation of ChinaNational Natural Science Foundation of China (NSFC) [51804017, 51974012]; China Postdoctoral Science FoundationChina Postdoctoral Science Foundation [2018M631341]; Open Fund of Key Laboratory of Ministry of Education for Efficient Mining and Safety of Metal Mines [USTBMSLAB201804]; Fundamental Research Funds for Central UniversitiesFundamental Research Funds for the Central Universities [FRF-TP-17-075A1]This work was financially supported by the National Natural Science Foundation of China (Grant numbers 51804017 and 51974012), the China Postdoctoral Science Foundation (Grant number 2018M631341), the Open Fund of Key Laboratory of Ministry of Education for Efficient Mining and Safety of Metal Mines (Grant number USTBMSLAB201804) and the Fundamental Research Funds for Central Universities (Grant number FRF-TP-17-075A1). the authors want to sincerely acknowledge the technical assistance provided in the laboratory