Actinomycetes are important producers of antibiotics and other important bioactive substances. Extraordinary ecosystems cause the evolution of novel secondary metabolic pathways of Actinomycetes, and increase the discovery possibility of new biological functions of bioactive compounds. Here, we isolated a rare Actinomycete from the soil samples of Cactus rhizosphere. An antagonistic Actinomycete strain (named SCA3-4) was screened against Fusarium oxysporum f. sp. cubense Tropical Race 4 (Foc TR4, ATCC 76255). The strain produced Pink-white aerial mycelia and brown substrate mycelium on gause No. 1 agar. Biverticillate chains of cylindrical spores were detected by scanning electron microscope (SEC). Analysis of the 16S rRNA sequence and a phylogenetic tree exhibited that the SCA3-4 strain shared a 99.54% similarity with Streptoverticillium lilacinum NRRL B-1968T and clustered into the same branch. Based on morphological, biochemical, physiological and molecular characteristics, the SCA3-4 strain was identified as Streptoverticillium sp. It can grow well on the different antibiotic medium with chloramphenicol, streptomycin, penicilin-G, gentamicin, erythromycin or neomycin sulfate. The PCR amplification of type I and Ⅱ polyketide synthase genes (PKS-I and PKS-Ⅱ) supported that the SCA3-4 strain owned the possible antimicrobial activity. Ethyl acetate extracts of the SCA3-4 strain showed a broad-spectrum antifungal activity against 13 plant pathogenic fungi including Foc TR4 and F. oxysporum f. sp. Cubense race 1 (ACCC 31271). The results of transmission electron microscope (TEM) showed that the crude extracts at the concentration 100 μg/ml inhibited spore germination and growth of Foc TR4 fungal spores by destroying cell membrane. 21 different compounds were identified from ethyl acetate extract of SCA3-4 strain by Gas Chromatography-Mass Spectrometry (GC-MS). These compounds were comprised of phenolic compound, pyrrolizidine, hydrocarbons, esters, and acids. Some compounds were already reported to possess antimicrobial or other biological activities. Other compounds with no functional annotation will be paid more and more attention to the discovery of new bioactive substances in the future.

Taxonomy and Broad-Spectrum Antifungal Activity of Streptomyces sp. SCA3-4 Isolated From Rhizosphere Soil of Opuntia stricta.

Actinobacteria is as a group of advanced filamentous bacteria. Rare Actinobacteria are of special interest as they are rarely isolated from the environments. They are a major source of important bioactive compounds. Determining the proper strategy for the identification of Actinobacteria harboring biosynthetic gene clusters and producing bioactive molecules is a challenging platform. In this review, we discuss a consequence of microbiological and molecular methods for the identification of rare Actinobacteria. In addition to that, we shed light on rare Actinobacteria’s significance in antibiotic production. We also clarified molecular approaches for the manipulation of novel biosynthetic gene clusters via PCR screening, fosmid libraries, and Illumina whole-genome sequencing in combination with bioinformatics analysis. Perceptions of the conventional and molecular identification of Actinobacteria were conducted. This will open the door for the genetic manipulation of novel antibiotic gene clusters in heterologous hosts. Also, these conclusions will lead to constructing new bioactive molecules via genetically engineering biosynthetic pathways.

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Microbiological and molecular insights on rare Actinobacteria harboring bioactive prospective

Potato is prone to many drastic diseases like potato common scab (CS). As no highly effective methods exist for managing CS, this study explored the possibility of using biological control. Ten bacterial strains were isolated from CS-infected potato tubers from four different locations of Punjab, Pakistan, and identified based on biochemical and molecular analysis. Analysis of 16s rDNA sequences amplified by PCR revealed the isolated bacterial strains to be Streptomyces scabies, S. turgidiscabies and S. stelliscabiei. Pathogenic islands were also confirmed among the isolates after identification of txtAB, nec1, and tomA genes with PCR amplification. One strain isolated from soil was antagonistic to the pathogenic Streptomyces spp., and determined to be Streptomyces A1RT on the basis of 16s rRNA sequencing. A methanolic extract of Streptomyces A1RT contained Isatropolone C, which was purified and structurally determined by 1H- and 13C-NMR, 1H/1H-COSY, HMQC, and HMBC techniques. Streptomyces A1RT also produced the plant growth hormone indole-3-acetic acid (IAA) with a titer of 26 μg ml-1 as confirmed by spectrophotometry and HPLC. In a greenhouse assay, disease severity index was established from 0 to 500. Average disease severity indexes were recorded as 63, 130.5, and 78 for Streptomyces scabies, S. turgidiscabies and S. stelliscabiei, respectively. When Streptomyces A1RT was applied in soil that contained one of these pathogenic isolates, the average disease severity indexes were significantly (P < 0.05) reduced to 11.1, 5.6 and 8.4, respectively. A significant increase in tuber weight and shoot development was also observed with the tubers treated with Streptomyces A1RT. The use of the plant growth-promoting Streptomyces A1RT against potato CS thus provides an alternative strategy to control the disease without affecting environmental, plants, animals and human health.

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Biological Control of Potato Common Scab With Rare Isatropolone C Compound Produced by Plant Growth Promoting Streptomyces A1RT.

A new bacterial strain, designated 452T, was isolated from the rhizosphere soil of the mangrove Avicennia marina in China. As determined, its cell wall peptidoglycan contained LL-diaminopimelic acid; MK-9(H8) and MK-9(H6) were the major isoprenoid quinones; and iso-C16:0 (31.3%), anteiso-C15:0 (16.9%), and iso-C15:0 (12.5%) were the major cellular fatty acids (>10.0%). Phylogenetic analysis based on the 16S rRNA gene sequence revealed that strain 452T formed a distinct lineage in the clade of the genus Streptomyces, and was closely related to S. coerulescens DSM 40146T (99.6% sequence identity), S. bellus DSM 40185T (99.5%), and S. coeruleorubidus DSM 41172T (99.3%). The DNA-DNA relatedness between strain 452T and these type strains ranged between 29.3 and 42.3%. Based on the phenotypic, chemotaxonomic, and phylogenetic features, the strain 452T is considered to represent a novel species of the genus Streptomyces, for which the name Streptomyces nigra sp. nov. is proposed. The type strain is 452T (=KCTC 39960T = MCCC 1K03346T). Further, strain 452T extracts exhibited a pronounced antitumor activity against human cancer cell lines A549, HCT-116, and HepG2, but not against normal human colon cells CCD-18Co. Active substances in the fermentation broth of strain 452T were isolated by bioassay-guided analysis, and then purified using a macroporous resin, silica gel, sephadex LX-20 column, and semi-preparative high-performance liquid chromatography (HPLC). Eight proline-containing diketopiperazines, namely, cyclo(Pro-Ala), cyclo(Pro-Gly), cyclo(Pro-Phe), cyclo(Pro-Met), cyclo(Pro-Val), cyclo(Pro-Leu), cyclo(Pro-Tyr), and cyclo(L-Leu-trans-4-hydroxy-L-Pro), were identified by electrospray ionization mass spectrometry (MS) and nuclear magnetic resonance (NMR). The compounds displayed different levels of cytotoxicity. The highest cytotoxicity was exhibited by cyclo(Pro-Ala) and cyclo(Pro-Met) against A549 cells, and cyclo(Phe-Pro) and cyclo(Pro-Ala) against HCT-116 cells, with average IC50 values equal to 18.5, 27.3, 32.3, and 47.6 μg/mL, respectively. The diversity of diketopiperazines and other chemicals produced by 452T was further investigated using gas chromatography (GC)-MS and liquid chromatography (LC)-MS. The analysis revealed 16 types of metabolites with antitumor activity and 16 other types of diketopiperazines. Hence, extracts of the newly identified strain may be used a starting material for the development of antitumor agents.

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Streptomyces nigra sp. nov. Is a Novel Actinobacterium Isolated From Mangrove Soil and Exerts a Potent Antitumor Activity in Vitro.

Streptomyces griseocarneus R132 controls phytopathogens and promotes growth of pepper (Capsicum annuum)

The occurrence of extensive antibiotics resistant bacteria increased the demands for mining out new sources of antimicrobial agents. Actinomycetes, especially Streptomyces sp. have grasped considerable attention worldwide due to production of many useful bioactive metabolites. In the present study, a total of 52 actinomycetes were isolated from agricultural soil samples in Beni-Suef, Egypt. All isolates were characterized based on colony morphology, mycelium coloration, and pigment diffusion. They were screened for their capabilities to show antimicrobial activities against different indicator microorganisms, and only 20 isolates have shown significant antimicrobial activities against at least one of the tested indicator microorganisms. The isolate AGM12-1 was active against all tested microorganisms and showed a marked antitumor activity with IC50 3.3 and 1.1μg/ml against HCT-116 and HepG-2 cell lines respectively. It was genotypically characterized as Streptomyces sp. with the presence of PKS Π biosynthetic gene cluster. Mannitol, ammonium sulfate, pH 7, 2% inoculum size and incubation for 11 days at 30 °C were the optimum conditions that used to maximize the production and hence allowed purification of one active antimicrobial compound to homogeneity using HPLC with a molecular mass of m/z 488.05. NMR structural elucidation showed that this compound was a diketopiperazine derivative.

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Exploring the Antimicrobial and Antitumor Potentials of Streptomyces sp. AGM12-1 Isolated from Egyptian Soil.

In this study, a thermo-tolerant isolated Bacillus licheniformis WF67 has produced considerable levels from the extracellular α-amylase under submerged fermentation conditions. To maximize the α-amylase production, both traditional “one factor per time” and statistical optimization were performed. The “one factor per time” optimization technique declared the most effective parameters in the process of α-amylase production. Those parameters were cultivation medium pH value, incubation time, soluble starch and beef extract as carbon and nitrogen sources. Response surface methodology (RSM) was employed to get the effective values of those most efficient parameters via different interaction ratios between all of them. Central composite design (CCD) was based on the following values: medium pH (pH 3.0–9.0), incubation time (15–75 h), soluble starch (1.5–19.5 g/L), and beef extract (1.0–13 g/L). Results obtained from CCD approach revealed that the incubation of B. licheniformis WF67 for 50 h, at pH value of 6.33, using the specified medium containing 12.55 g/L soluble starch, and 8.31 g/L beef extract were the optimum values for α-amylase production. Under the previously mentioned conditions α-amylase productivity was improved by about 90% (6.633 U/mL) in comparison to the traditional “one factor per time” optimization results (3.486 U/mL).

Response surface methodology as an approach for optimization of α-amylase production by the new isolated thermotolerant Bacillus licheniformis WF67 strain in submerged fermentation

This study contains evidence-based recommendations for the prevention of hospital acquired infections. Hospital acquired infections are a major cause of mortality and morbidity and provide challenge to clinicians. Measures of infection control included identifying patients at risk of nosocomial infections. Antiseptics and disinfectants are used extensively in hospitals and other health care settings for a variety of topical and hard-surface applications. In particular, they are an essential part of infection control practices and aid in the prevention of nosocomial infection. This study investigated the nosocomial infection via isolation and identification of bacterial pathogens, the effect of detergents against isolated bacteria, and describes the histopathological tissue changes induced by the isolated bacteria in vivo study. Some bacteria resistant to disinfectants were prevalent and these bacteria had different effects on the human, Different pathological changes were seen experimentally by inoculation of these bacteria in mice.

https://jvmr.journals.ekb.eg/article_43326_5a9d41189be2fdb6d9e832267c0acb4d.pdf

Maged S. Ahmad

Papers

Exploring the Antimicrobial and Antitumor Potentials of Streptomyces sp. AGM12-1 Isolated from Egyptian Soil.

Response surface methodology as an approach for optimization of α-amylase production by the new isolated thermotolerant Bacillus licheniformis WF67 strain in submerged fermentation

Nosocomial Antiseptics And Disinfectants Resistant Bacteria: microbiological and histopathological studies