Streptomyces Alboflavus Research Articles

Potential of growth-promoting bacteria in maize (Zea mays L.) varies according to soil moisture

Climate change has caused irregularities in water distribution, which affect the soil drying-wetting cycle and the development of economically important agricultural crops. Therefore, the use of plant growth-promoting bacteria (PGPB) emerges as an efficient strategy to mitigate negative impacts on crop yield. We hypothesized that the use of PGPB (in consortium or not) had potential to promote maize (Zea mays L.) growth under a soil moisture gradient in both non-sterile and sterile soils. Thirty PGPB strains were characterized for direct plant growth-promotion and drought tolerance induction mechanisms and were used in two independent experiments. Four soil water contents were used to simulate a severe drought (30% of field capacity [FC]), moderate drought (50% of FC), no drought (80% of FC) and, finally, a water gradient comprising the three mentioned soil water contents (80%, 50%, and 30% of FC). Two bacteria strains (BS28–7 Arthrobacter sp. and BS43 Streptomyces alboflavus), in addition to three consortia (BC2, BC4 and BCV) stood out in maize growth performance in experiment 1 and were used in experiment 2. Overall, under moderate drought, inoculation with BS43 surpassed the control treatment in root dry mass and nutrient uptake. Considering the water gradient treatment (80–50–30% of FC), the greatest total biomass was found in the uninoculated treatment when compared to BS28–7, BC2, and BCV. The greatest development of Z. mays L. was only observed under constant water stress conditions in the presence of PGPB. This is the first report that demonstrated the negative effect of individual inoculation of Arthrobacter sp. and the consortium of this strain with Streptomyces alboflavus on the growth of Z. mays L. based on a soil moisture gradient; however, future studies are needed for further validation.

Streptomyces typhae sp. nov., a novel endophytic actinomycete with antifungal activity isolated the root of cattail (Typha angustifolia L.).

A novel endophytic actinomycete with antagonistic activity against various phytopathogenic fungi, designated strain p1417T, was isolated from the root of cattail (Typha angustifolia L.) collected from Yunnan Province, Southwest China. A polyphasic taxonomic study was carried out to establish the taxonomic status of this strain. Strain p1417T was found to have morphological and chemotaxonomic characteristics typical of the genus Streptomyces. The diamino acid present in the cell wall was LL-diaminopimelic acid. Xylose and arabinose occurred in whole cell hydrolysates. The menaquinones were identified as MK-9(H8), MK-9(H6) and MK-9(H4). The polar lipid profile was found to contain diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol and phosphatidylinositol mannoside. The major fatty acids were found to be iso-C16:0, anteiso-C15:0, iso-C15:0 and C16:0. The genomic DNA G + C content of strain p1417T based on the genome sequence was 72.0mol%. Based on 16S rRNA gene, five housekeeping genes and whole genome sequences analysis, strain p1417T was most closely related to Streptomyces flavofungini JCM 4753T (99.4% 16S rRNA gene sequence similarity), Streptomyces alboflavus JCM 4615T (98.8%) and Streptomyces aureoverticillatus JCM 4347T (98.2%). However, the average nucleotide identity values, the digital DNA-DNA hybridization values and the multilocus sequence analysis evolutionary distances between this strain and its closely related strains showed that it belonged to one distinct species. In addition, these results were also supported by differences in the phenotypic and chemotaxonomic characteristics between strain p1417T and three closely related type strains. Therefore, it is concluded that strain p1417T represents a novel species of the genus of Streptomyces, for which the name Streptomyces typhae sp. nov. is proposed. The type strain is p1417T (= CCTCC AA 2019091T = DSM 110636T).

Discovery of Brominated Alboflavusins With Anti-MRSA Activities.

As methicillin-resistant Staphylococcus aureus (MRSA) is becoming a serious pathogenic threaten to human health worldwide, there is an urgent need to discover new antibiotics for the treatment of MRSA infections. Alboflavusins (AFNs) are a group of halogenated cyclohexapeptides with anti-MRSA activities. In this study, two novel brominated AFN congeners (compounds 1 and 2) were isolated from the wild-type strain Streptomyces alboflavus sp. 313 that was fermented in the production medium supplemented with NaBr; two new (compounds 3 and 5) and a known (compound 4) dehelogenated AFN congeners were isolated from S. alboflavus ΔafnX, in which the tryptophan halogenase gene afnX was inactivated. The structures of these compounds were assigned by careful NMR and MS analyses. The anti-MRSA activities of varied AFN congeners were assessed against different MRSA strains, which revealed that compounds 1 and 2 with bromine displayed effective activities against the tested MRSA strains. Especially, compound 2 showed good anti-MRSA activity, while compounds 3, 4, and 5 without halogen exhibited weak anti-MRSA activities, outlining the influence of halogen substitution to the bioactivities of AFNs.

Bacteria from tropical semiarid temporary ponds promote maize growth under hydric stress

World climate change has triggered soil water stress and imposed limitations on agricultural production. Plant growth-promoting bacteria (PGPBs) have been an efficient strategy to improve the biological supply and growth of plants under distinct abiotic stress conditions. We hypothesized that the soils from a temporary pond may harbor PGPBs with potential strains which increase maize tolerance to water deficit. We studied rhizosphere and bulk soil of Mimosa bimucronata in a temporary pond from semiarid Northeast Brazil to access strains with characteristics to promote plant growth and mitigate abiotic stress for maize crop. We isolated 355 bacterial isolates, from which 96 were selected based on the morphophysiological characterization to assess IAA production (42 % produced over 50 μg mL-1 of IAA), calcium phosphate solubilization (with one isolate achieving medium IS), biofilm and exopolysaccharides production (66 % and 98 % of isolates, respectively). Based on these mechanisms, the 30 most promising bacterial isolates were selected to assess biological nitrogen fixation (74 % of the isolates showed nitrogenase activity greater than 20 C2H4.h-1.mg-1), ACC deaminase activity (80 % of isolates) and growth in medium with reduced water activity (8 % of isolates grew in medium with water activity (Aw) of 0.844). We sequenced the 16S rRNA gene from the seven most promising isolates in in vitro and in vivo assays, which were identified as Staphylococcus edaphicus, Bacillus wiedmannii, Micrococcus yunnanensis, Streptomyces alboflavus, Streptomyces alboflavus, Bacillus wiedmanni and Bacillus cereus. In vivo, eleven isolates and three bacterial consortia did not differ from the control with nutrient solution, for total leaf area and root dry mass of maize. S. alboflavus (BS43) had the best in vivo results, not differing from the control with nutrient solution. We highlight the unpublished potential of Staphylococcus edaphicus and Streptomyces alboflavus in promoting the growth of plants under water stress. In addition, it is the first report of bacteria isolated from a temporary pond in the Brazilian semiarid which promoting plant growth attributes and development.

The antibiotic activity and mechanisms of active metabolites (Streptomyces alboflavus TD-1) against Ralstonia solanacearum.

In order to elucidate the antibacterial activity and mechanism of S. alboflavus TD-1 active metabolites, the minimal inhibitory concentration of R. solanacearum and other effects on cell wall, cell membrane, nucleic acid, protein and cell morphology were studied. Besides, based on LCMS-IT-TOF, the active metabolites of S. alboflavus TD-1 were preliminarily analyzed. In this study, We found that the active metabolites had obvious inhibitory effect on R. solanacearum, and the minimal inhibitory concentration (MIC) of R. solanacearum was 3.125mg/mL. And the treatment of 10mg/mL active metabolites can increase the permeability of R. solanacearum membranes, destroy the cell wall integrity, inhibit the synthesis of bacterial nucleic acids and proteins, and cause leakage of bacterial nucleic acids and proteins, obstruct the normal expression of proteins and destroy their bacterial morphology. At the same time, We speculated the molecular weights corresponding to the six compounds were 618, 615, 615, 615, 646, 646, respectively among the active metabolites, and it was found that were highly unstable. The active metabolites produced by S. alboflavus TD-1 liquid fermentation contain components that can significant inhibitory effects on R. solanacearum. It had the potential to develop biocontrol agents against bacterial wilt and be a kind potential sources for the preparation of functional anti-pathogenic microbial agents.

Biofumigation with volatile organic compounds from Streptomyces alboflavus TD‐1 and pure chemicals to control Aspergillus ochraceus

The antagonistic activity of volatile compounds from Streptomyces alboflavus TD‐1 against Aspergillus ochraceus were investigated in this study. Conidial germination and mycelial growth of A. ochraceus were completely suppressed after exposure to 40 and 80 g/L of wheat bran cultures of S. alboflavus TD‐1. A total of 35 compounds (relative peak area [RA] >0.10) were identified from wheat bran cultures of S. alboflavus TD‐1. Five standard compounds were purchased for the antifungal activity assay: anisole, dimethyl trisulfide, β‐pinene, benzenamine and 1,5‐cyclooctadiene. Among these, dimethyl trisulfide and benzenamine showed strong inhibitory effects on the mycelial growth of A. ochraceus. In addition, conidial and hyphal morphological abnormalities were observed in treated A. ochraceus. Scanning electron microscopy (SEM) and OD‐260 nm absorption analysis demonstrated that disruption of membrane integrity may be a possible mechanism of action for volatiles from S. alboflavus TD‐1. This study indicates that volatiles of S. alboflavus TD‐1 have tremendous potential to act as a strategy for the biocontrol of postharvest diseases in food during storage.

Streptomyces lasiicapitis sp. nov., an actinomycete that produces kanchanamycin, isolated from the head of an ant (Lasius fuliginosus L.).

During a screening for novel and biotechnologically useful actinobacteria in insects, a kanchanamycin-producing actinomycete with antifungal activity, designated strain 3H-HV17(2)T, was isolated from the head of an ant (Lasius fuliginosus L.) and characterized using a polyphasic approach. 16S rRNA gene sequence similarity studies showed that strain 3H-HV17(2)T belongs to the genus Streptomyces with the highest sequence similarities to Streptomyces spectabilis NBRC 13424T (98.90 %, with which it phylogenetically clustered, Streptomyces alboflavus NRRL B-2373T (98.65 %) and Streptomyces flavofungini NBRC 13371T (98.36 %). Phylogenetic analysis based on the gyrB gene also supported the close relationship of these strains. The morphological and chemotaxonomic properties of the strain are also consistent with those members of the genus Streptomyces. A combination of DNA-DNA hybridization experiments and phenotypic tests were carried out between strain 3H-HV17(2)T and its phylogenetically closely related strains, which further clarified their relatedness and demonstrated that strain 3H-HV17(2)T could be distinguished from these strains. Therefore, strain 3H-HV17(2)T is concluded to represent a novel species of the genus Streptomyces, for which the name Streptomyces lasiicapitis sp. nov. is proposed. The type strain is 3H-HV17(2)T (=CGMCC 4.7349T=DSM 103124T).

Phenol degradation studies using microbial consortium isolated from environmental sources

A microbial consortium consisting of five phenol-degrading strains was developed. The consortium could degrade 99% of 1000mgl−1 phenol after 72h incubation with a biomass increase of 2.6×107 to 4×1012CFUml−1. Characterization of the members revealed that consortium consisted of Candida tropicalis (1.2×105CFUml−1), Aspergillus fumigatus (1.1×105CFUml−1), Candida albicans (3.0×103CFUml−1), Candida haemulonis (2.6×103CFUml−1) and Streptomyces alboflavus (1.1×105CFUml−1). Performance of consortium was accessed by specific growth rate (μ) and yield coefficient (Yx/s). The consortium exhibited activity of phenol hydroxylase and catechol 1,2-dioxygenase suggesting that members in consortium followed ortho pathway for phenol degradation. Response surface methodology (RSM) has been adopted to evaluate the effect of different parameter such as initial phenol concentration, temperature, pH and time on phenol degradation. The maximum percentage of phenol degradation is observed at optimized value of process variables such as initial concentration 1000mgl−1, temperature 35°C, pH 7 and incubation time of 96h.

Combination of uniform design with artificial neural network coupling genetic algorithm: an effective way to obtain high yield of biomass and algicidal compound of a novel HABs control actinomycete.

Controlling harmful algae blooms (HABs) using microbial algicides is cheap, efficient and environmental-friendly. However, obtaining high yield of algicidal microbes to meet the need of field test is still a big challenge since qualitative and quantitative analysis of algicidal compounds is difficult. In this study, we developed a protocol to increase the yield of both biomass and algicidal compound present in a novel algicidal actinomycete Streptomyces alboflavus RPS, which kills Phaeocystis globosa. To overcome the problem in algicidal compound quantification, we chose algicidal ratio as the index and used artificial neural network to fit the data, which was appropriate for this nonlinear situation. In this protocol, we firstly determined five main influencing factors through single factor experiments and generated the multifactorial experimental groups with a U15(155) uniform-design-table. Then, we used the traditional quadratic polynomial stepwise regression model and an accurate, fully optimized BP-neural network to simulate the fermentation. Optimized with genetic algorithm and verified using experiments, we successfully increased the algicidal ratio of the fermentation broth by 16.90% and the dry mycelial weight by 69.27%. These results suggested that this newly developed approach is a viable and easy way to optimize the fermentation conditions for algicidal microorganisms.

Streptomyces alboflavus RPS and Its Novel and High Algicidal Activity against Harmful Algal Bloom Species Phaeocystis globosa

Phaeocystis globosa blooms have frequently occurred along coastal waters and exerted serious impacts on ecological environments by releasing toxic hemolytic substances, forming nuisance foam, and causing oxygen depletion. An actinomycete strain RPS with high algicidal activity against P. globosa was isolated and identified as Streptomyces alboflavus, based on morphology, physiological and biochemical characteristics, and 16S rDNA sequence analysis. RPS lysed 95% of P. globosa within 48 h by releasing an extracellular active substance into the growth medium. The activity of RPS supernatant was sensitive to temperature at and above 50°C and insensitive to pH from 3 to 11. The molecular weight of the active substance was between 100 Da and 1000 Da, and approximately 90% of it was extracted by ethyl acetate. It was presumed that the active component efficiently inhibited the movement of P. globosa, caused the flagella to fall off the algae, and finally lysed the algal cells. RPS showed a wide target range against harmful algae. S. alboflavus RPS with high algicidal activity and such novel features of temperature and pH sensitivity, low molecular weight, algicidal process, and target range possesses great potential in the biological control of P. globosa blooms.

English

An actinomycete, isolated from soil samples of western Sichuan Plateau of China, was identified as Streptomyces alboflavus SC11 by 16S rDNA analysis, and also cultural, morphological and physiological characteristics of the strain were recorded. From the fermentation broth of the strain, an antimicrobial ingredient was isolated and elucidated as desertomycin A, mainly by analysis of electrospray ionization tandem mass spectrometry (ESI-MS/MS), 1H nuclear magnetic resonance (NMR) and 13C NMR spectra data. Desertomycin A exhibited good antimicrobial potential against the pathogenic bacteria and fungi. Minimum inhibition concentration (MIC) values of desertomycin A were 3.9, 7.8 and 7.8 μg/ml against Bacillus cereus, Bacillus subtilis and Staphyloccocus aureus,respectively.   Key words: Streptomyces alboflavus SC11,Desertomycin A, 16S rDNA, Antimicrobial activities.      

Antifungal activity of volatile organic compounds fromStreptomyces alboflavusTD-1

Streptomyces sp. TD-1 was identified as Streptomyces alboflavus based on its morphological characteristics, physiological properties, and 16S rDNA gene sequence analysis. The antifungal activity of the volatile-producing S. alboflavus TD-1 was investigated. Results showed that volatiles generated by S. alboflavus TD-1 inhibited storage fungi Fusarium moniliforme Sheldon, Aspergillus flavus, Aspergillus ochraceus, Aspergillus niger, and Penicillum citrinum in vitro. GC/MS analysis revealed that 27 kinds of volatile organic compounds were identified from the volatiles of S. alboflavus TD-1 mycelia, among which the most abundant compound was 2-methylisoborneol. Dimethyl disulfide was proved to have antifungal activity against F. moniliforme by fumigation in vitro.

NW-G01, a novel cyclic hexadepsipeptide antibiotic, produced by Streptomyces alboflavus 313: I. Taxonomy, fermentation, isolation, physicochemical properties and antibacterial activities

NW-G01, a novel cyclic hexadepsipeptide antibiotic, was isolated by macroporous resin and silica gel column chromatography and HPLC from the fermentation broth of strain no. 313. The producing strain was identified as Streptomyces alboflavus on the basis of the morphological characteristics, physiological property and 16S rDNA gene sequence analysis. NW-G01 exhibited strong antibacterial activity against Bacillus subtilis, Bacillus cereus, Staphylococcus aureus, methicillin-resistant S. aureus, and their MIC values were 3.90, 3.90, 7.81 and 7.81 microg ml(-1), respectively.

Studies on microbial antagonism in rhizosphere soils of potato varieties differentially susceptible to black-scurf and wilt

The antagonistic microflora in the rhizosphere of plants of three varieties of potato, viz. Ps 194' ‘Up to date’, and a local variety of different ages were analysed. Antagonists were selected either by random isolation or by Wilska's spraying technique. The antagonists were always found in higher frequency in rhizosphere compared with the control soil. The highest percentage of actinomycetes antagonists were found in the variety Up to date; of fungal antagonists in the variety Ps 194; while the local variety was found to be the poorest in this regard. Further, the antagonistic activity of these organisms was estimated by a cross-streak method and the resistant antagonists were also selected by cross-antagonism. The most resistant antagonists found were Trichoderma viride T 56 and T 7, Chaetomium trilaterate F 75, Streptomyces alboflavus Rs 40, Streptomyces sp. Cs 73, Pseudomonas sp. Rs 1 50 and Pseudomonas sp III Ps 63.