Abstract:Research on the metabolites of myxomycetes has previously demonstrated the high potential for practical applications and has made great progress. In this paper, we reviewed more than 100 metabolites isolated from myxomycetes, including fatty acids, amino acids, alkaloids, naphthoquinones, aromatic compounds, terpenoids, esters or derivatives thereof. We also introduced their antimicrobial, antitumor, cytotoxic and antioxidant activities. In addition, the structure-activity relationship of these compounds has been briefly introduced. Furthermore, the biological activity research methods and biochemical characteristics of myxomycetes were also summarized, whilst the differences between the metabolites of various myxomycetes were analyzed. Finally, the problems and prospects of myxomycetes metabolites research have been discussed.

Abstract:Microbial electron transfer plays a key role in microbial metabolism and the biogeochemical cycle. The direct contact-dependent microorganism extracellular electron transfer i.e. direct extracellular electron transfer process has become a common focus in different subjects including but not limited to microbiology, geochemistry and biophysics. A series of significant novel findings and theoretical breakthrough in direct extracellular electron transfer have been reported in recent years, such as the molecular explanation of direct extracellular electron transfer, discovery of microbial nanowires and cable bacteria. Along with these new progresses, more problems arise to be addressed, including a more specified direct extracellular electron transfer mechanism in different microbes, effects of direct extracellular electron transfer on the neighbor species and local environment. A cross application of multi-disciplinary theories and technologies is a key to further reveal the process of direct extracellular electron transfer.

Abstract:Streptomyces have a unique and complex morphological differentiation process. The process of aerial hyphae differentiating into spore filaments is accompanied by the biosynthesis of secondary metabolites. The morphological differentiation of Streptomyces involves many steps, such as chromosome replication, condensation and separation. As important components of chromosome structure and the global regulatory factors of bacteria, the nucleoid-associated proteins play an important role in the regulation of morphological differentiation and secondary metabolism of Streptomyces. In this paper, we summarize the structures, functions, regulation of nucleoid-associated proteins and especially their role in morphological differentiation and secondary metabolism of Streptomyces.

Abstract:[Objective] To identify the capacity that the structural protein VP1 of foot-and-mouth disease virus potentially accommodate insertion of different foreign tags, we constructed recombinant FMDVs containing foreign tags using FMDV reverse genetics system. [Methods] Using overlap extension PCR method, we introduced V5, TC12, KT3, 3×FLAG tag genes into G-H loop of VP1 capsid protein of FMDV. Linearized recombinant plasmids were transfected into BSR/T7 cells expressing T7 RNA polymerase to rescue the recombinant viruses. The recombinant viruses were analyzed by RT-PCR, indirect immunofluorescence, plaque phenotype and one-step growth curves. [Results] We successfully rescued the recombinant FMDVs expressing V5 and KT3 tag but could not rescue the recombinant FMDV containing TC12 and 3×FLAG tags. The introduction of V5 and KT3 tags both affected the replication capacity of FMDV. [Conclusion] Our results will lay foundations to study marker vaccine and FMDV vector in future.

Abstract:[Objective] Our aim is to screen efficient organophosphate-degradation bacteria from environment and study their growth promoting mechanism. [Methods] We screened organophosphate-degradation bacteria from environment using selective medium, and studied the promoting growth characteristics by biochemical assays, then screened organophosphate-degradation and plant-growth-promoting bacteria by pot experiment. [Results] In total 35 strains of organophosphate-degradation bacteria were isolated from bulk soil of grass by Mengjinna organophosphate-degradation medium. The promoting growth characteristics of these bacteria were checked by biochemical methods. Five representative strains were selected for cucumber seedlings pot experiment. Strain G3-6 had the strongest ability to solubilize organic phosphorus, the ratio of hydrolysis circle diameter (HD) and colony diameter (CD) was 3.28. Strain G3-6 had the highest ability to promote cucumber growth than other strains. Compared with the control, G3-6 increased fresh weight, dry weight and height of cucumber seedlings by 71.53%, 69.78% and 33.55%, respectively. Compared with the positive control Bacillus subtilis F-H-1, G3-6 increased fresh weight, dry weight and height of cucumber seedlings by 2.52%, 21.14% and 8.27%, respectively. The results of correlation analysis showed that the ability of organophosphate-degradation might play a more important role in promoting cucumber growth than other functions. Strain G3-6 was identified as Pseudomonas sp. by 16S rRNA analysis. [Conclusion] Pseudomonas sp. G3-6 has strong ability of depredating organic phosphate, and can strongly promote cucumber growth. This strain would be a potential growth promoting bacterium.

Abstract:[Objective] We explored the role of mobile plasmids in transferring antimicrobial resistant genes in extended-spectrum beta-lactamases (ESBLs)-producing Escherichia coli from a wastewater treatment plant. [Methods] Based on the conjugation experiments of ESBL-producing E. coli collected from wastewater, the disk diffusion assay and polymerase chain reaction (PCR) were used to determine the transfer of antimicrobial resistance. [Results] A total of 50 ESBL-producing E. coli were collected from 80 water samples (50/80, 62.5%), and successful conjugations were detected among 35 isolates (35/70, 70.0%). The results of PCR further showed that bla_CTX-M and bla_TEM genes were all capable of conjugation transfer, but the horizontal transfer of bla_SHV gene was only detected in one isolate and resistance gene encoding fluoroquinolone was not capable of conjugation transfer in this study. [Conclusions] Plasmids carrying different antimicrobial resistant genes may exhibit different capacity of horizontal transfer. Importantly, the mobile plasmids played a very important role in the horizontal transfer of antimicrobial resistance genes of ESBL-producing E. coli.

Abstract:[Objective] To explore the application potential of three marine Trichoderma spp. as biocontrol agents and bio-fertilizer. [Methods] Three Trichoderma spp. with high antimicrobial activity and spore germination were selected by isolating, screening and mutagenesis. Several indicators related with application potential of these strains were tested. Sporulation capacity was measured after optimizing culture medium, temperature and initial pH. Antimicrobial activity was evaluated based on inhibition spectrum, superparasitism and related antifungal genes. Special culture method was used to determine the secretion of cellulase, phytase and siderophore, and the ability to release phosphorus and potassium. High performance liquid chromatography was used to quantify indole-3-acetic acid production. [Results] We obtained three Trichoderma spp. with the spore germinations of 3.45×10⁸, 3.10×10⁸ and 2.55×10⁸ CFU/cm², respectively. Moreover, these mutants formed chlamydospores, and strain XG20-1 had the highest chlamydospore germination of 3.56×10⁸ CFU/mL. All three strains showed a broad inhibition spectrum against 6 fungal phytopathogen and the superparasitism to Alternaria solani. Moreover, Tex1, Nag1 and Eg1 genes were found in all strains, with cellulose, phytase and siderophore detected. Indole-3-acetic acid productions in three strains were 2.61, 1.57 and 1.92 mg/L, respectively, and all three strains had the capacity of releasing phosphorus and potassium. [Conclusion] Three Trichoderma spp. had high antimicrobial activities against plant pathogenic fungi through integrated mechanism, high spore-bearing yields and growth-promoting effects on plants, which showed their potential application as biocontrol agents and bio-fertilizer.

Abstract:[Objective] The aim of this study was to identify bacterial species capable of degrading nicotine, and to characterize related genes. [Methods] One bacterial strain with the ability to degrade nicotine was screened from tobacco field soil by using nicotine as the sole carbon source. Using phylogenetic analysis of its 16S rRNA gene, together with physiological and biochemical characteristics, we identified this strain as Agrobacterium tumefacience SCUEC1. We determined its association of degradation rate with its growth rate, and its tolerance to nicotine. Also, the genome was sequenced using high throughput sequencing technology, and the nicotine metabolic pathway of SCUEC1 strain was analyzed by bioinformatics tools. [Results] Nicotine degradation rate of SCUEC1 reached 94.81%. The strain tolerated nicotine with the concentration from 0.50 g/L to 5.00 g/L. Its metabolic pathway of nicotine degradation appeared similar to that of Ochrobactrum sp. strain SJY1. [Conclusion] Agrobacterium tumerficience SCUEC1 degraded nicotine. These findings provide a theoretical basis for biodegradation of nicotine.

Abstract:[Objective] Using desirable strain resources to control Fusarium wilt of cotton is an effective way. This study aimed to acquire antagonistic endophytic bacteria from soybean nodules, explore their inhibition mechanism and strain characteristics. [Methods] Confrontation and metabolic liquid culture methods were adopted to screen endophytic bacteria from soybean nodules against Fusarium oxysporum f. sp. vasinfectum. The effect of screened strains on pathogen hyphae changes were analyzed with microscopic observation method. Combined with cultural, physical and chemical characteristics, 16S rDNA sequencing results and homology analysis of screened strains, phylogenetic status were determined. Disease-control effects were demonstrated by greenhouse inoculation test. [Results] Five strains of endophytes have inhibitory effect by the second screening and metabolic liquid test. Pathogen hyphae treated with endophytes became deformity, its cell wall disappeared, autolysis, bold at the base of the mycelium, branches increased and root shape appeared. Hyphae were embeded, dissolved and fractured by lawn formed by endophytic bacteria, and presented spherical expansion of its terminal. The inhibition of endophytic bacteria against Fusarium oxysporum f. sp. vasinfectum was mainly caused by extracellular metabolites. DD174, DD176 and DD179 were similar to Bacillus oceanisediminis H2^T(GQ292772) and B. thuringiensis ATCC 10792^T(AF290545), respectively. DD165 and DD166 were similar to Stenotrophomonas maltophilia LMG 958^T (X95923). DD174 tolerated 6% salt concentration and grew well at pH 10. Control effect of treatment group with DD174 was 76.32%, those of others were above 62%, so these strains can be used as biocontrol resources against Fusarium oxysporum f. sp. vasinfectum. [Conclusion] Endophytic antagonistic bacteria inhabited soybean root nodules against Fusarium oxysporum f. sp. vasinfectum.

Abstract:[Objective] Glarea lozoyensis is a filamentous fungus used for industrial production of the antifungal drug caspofungin. Previously, the mitochondrial genome (mitogenome) of a mutant strain ATCC 74030 was reported. The purpose of the current study is to test if mutagen treatments have caused changes on the mitogenome of the fungus. [Methods] The mitogenome of the wild strain ATCC 20868 was assembled and compared with the published mitogenome of ATCC 74030. PCR assays were done for both strains. Additional analyses were done using correct mitogenome sequences. [Results] We successfully assembled the mitogenome of the wild strain ATCC 20868. Initial comparison of the mitogenomes of the wild and mutant strains indicated six variable nucleotide sites and two regions with length variations. PCR assays and subsequent sequencing, however, showed no difference between the two strains. The differences observed from initial comparison were due to sequence errors present in the published mitogenome of ATCC 74030. Interestingly, three intron-containing tRNAs and a rnpB gene were detected in the mitogenome of the fungus. Obvious repetitive elements were identified within the G. lozoyensis mitogenome, and duplication events were identified between its mitochondrial and nuclear genomes. [Conclusion] We verified that there existed erroneous sequences in the published mitogenome of ATCC 74030; mutagens did not cause variations on the mitogenome of G. lozoyensis. We reported the authentic mitogenome sequence of G. lozoyensis and found frequent gene transfer between mitochondrial and nuclear genomes in the fungus.

Abstract:[Objective] We isolated and identified a protease producing bacterium from Rhizoma Imperatae. [Methods] The species and abundances of bacteria from Rhizoma Imperatae were determined by high-throughput sequencing. The protease producing strain was screened by using selective medium containing casein. Besides, the effects of environmental factors on bacterial growth and protease activity were determined by single factor experiment. [Results] A protease producing strain H-16 was isolated from selective medium and identified as Escherichia marmotae by physiological-biochemical experiments and 16S rDNA sequence analysis. Strain H-16 could produce a protease with molecular weight of about 70 kDa. Tryptone, sucrose, 30℃ or 35℃, and pH 7 were the optimum nitrogen source, carbon source, temperature, and pH, respectively, for the growth of strain H-16. The protease produced by strain H-16 exhibited optimum activity for casein between pH 6 and 8, and it did not lose much enzyme activity under the conditions of below 50℃ and less than 6% salinity. In addition, Cu(II), Ag(I), and other metal ions could inhibit the activity of the protease. [Conclusion] Strain H-16 could be a good candidate for protease production.

Abstract:[Objective] As a typical desert animal, camel can eat pungent poisonous plants that are not eaten by other animals, and without affecting their normal physiological metabolism. Many studies found that phytotoxic substances in plants eaten by camel have similar chemical structure to that of pyridine, quinolone, indole and other heterocyclic compounds. However, few studies explored the biodiversity of bacteria degrading potentially heterocyclic compounds in camel rumen. [Methods] We used pyridine, quinolone and indole as the only carbon and nitrogen resources, and five generations of enrichment culture method to cultivate camel rumen bacteria, and used high throughput sequencing (Illumina Miseq) to sequence the total DNA of the five generations culture broth. [Results] Proteobacteria, Actinobacteria, Bacteroidetes, Planctomycetes and Firmicutes constitute the highest abundance of five categories of camel rumen bacteria degrading heterocyclic compounds. The dominant bacteria of degrading pyridine, quinolone, indole may belong to Sphingobacterium and Acinetobacter, Bacillus, Lysinibacillus and Sphingobacterium. [Conclusion] Camel rumen has heterocyclic compounds degrading bacteria.

Abstract:[Objective] We studied the effects of lysozyme on in vitro rumen fermentation, methanogenesis and microbial community structure. [Methods] Lysozyme was added to in vitro ruminal cultures at 5 doses: with 0 (L-0, Control), 0.1 mg/100 mL (L-0.1), 1 mg/100 mL (L-1), 10 mg/100 mL (L-10), and 100 mg/100 mL (L-100). Total gas and methane production were measured at different time of incubation. Culture samples were collected at 24 h for analysis of fermentation parameters and functional microbial populations. In addition, samples of L-0, L-1, and L-100 collected at 24 h were also used subjected to metagenomics analysis of bacterial community using Illumina sequencing of 16S rRNA gene amplicons. [Results] Compared with control, methane production, ammonia concentration, dry matter digestibility, organic matter digestibility and total volatile fatty acid concentration were not influenced by L-0.1 (P>0.05). Methane production and NH₃-N concentration were reduced, and propionate concentration was increased by L-1 (P<0.05), whereas dry matter digestibility, organic matter digestibility or total volatile fatty acid were not affected (P>0.05). Methane production was reduced, and propionate concentration was increased by L-10 and L-100 (P<0.05), but dry matter digestibility and organic matter digestibility were also decreased significantly (P<0.05). The qPCR results showed that total bacteria, fungi and methanogens were significantly reduced by L-100 (P<0.05), but were not influenced (P>0.05) by L-0.1, L-1, or L-10. Principal Component Analysis of the sequencing data showed clear differences in the composition of the ruminal bacterial community between the control and the lysozyme treatments, demonstrating evident impact of the lysozyme addition. The abundance of propionate-producing bacteria (e.g., Selenomonas and Succinivibrio) was increased by lysozyme, resulting in more hydrogen being directed to production of propionate instead of methane. Moreover, the reduced ammonia concentration in L-1 was probably due to the lower abundance of proteolytic bacteria (e.g., Prevotella and Bacteroides) inhibited by lysozyme. [Conclusion] Appropriate lysozyme addition (1 mg/100 mL) can be used to modulate ruminal microbial ecology and reduce methanogenesis and ammoniagenesis by rumen microbiome without adversely affecting feed digestion or fermentation in short-term.s

Abstract:[Objective] This study aimed to explore the mechanism of fatty acid insertion during membrane synthesis when cells grow and divide in Escherichia coli. [Methods] In the phosphatidylethanolamine (PE) synthesis pathway, acetyl-CoA was used as the substrate to synthesize long-chain acyl-ACP, followed by the synthesis of PE. The ten enzymes involved were each fused with a fluorescent protein such as enhanced green fluorescent protein (EGFP) or monmer Cherry (mCherry), and the fusion proteins were expressed in E. coli. The localizations of the fusion proteins were detected by laser scanning confocal fluorescence microscopy. [Results] Fluorescent microscope images showed that the proteins EGFP-FabA, EGFP-FabB, EGFP-FabI, EGFP-FabG, EGFP-PlsB, and EGFP-PssA accumulated in the polar and septal regions when expressed at high levels. Therefore, the ten enzymes displayed different localization patterns at different expression levels. Time-lapse imaging showed that EGFP-PlsB accumulated in the septum before cell division, then these regions of division became poles of the new cells. [Conclusion] This indicates that fatty acid inserted at the septum for PE synthesis and then PE was transported to all the other membrane regions.