Control of Fusarium Wilt Using Streptomyces griseus with Plant Growth-Promoting Effect on Tomato

The efficacy of antagonistic Streptomyces griseus was evaluated against tomato wilt disease incited by Fusarium oxysporum. Among the different formulations, Streptomyces griseus with chitin amended formulation showed effective increase in seed germination and seedling vigour. Further, talc-based formulations of S. griseus mixed with or without chitin was developed and tested under greenhouse conditions. Lowest disease severity of 19.1% was observed in plants treated with self fusant (SFSg 5) S. griseus suspension (root dipping – 9 x 108 cfu / mL) followed by 19.5% in treatment of chitin amended S. griseus (root dipping – 9 x 108 cfu/mL) was recorded over control. Plant growth of the treated traits were analyzed and compared with control. The shoot length, root length, leaf area was increased significantly over the controls by the treatment of self fusant (SFSg 5) S. griseus suspension followed by nearby values were reached in chitin amended S. griseus was recorded. The chemical treatments had less effect compared with these formulations. Histochemical studies showed that cambium layers, xylem vessels per bundle, and the vessel diameter decreased in the plants inoculated with F. oxysporum over control and changes in variables were observed in infected plants treated with S. griseus. In conclusion, S. griseus can be a potential biocontrol agent against F. oxysporum for better crop production practices.

Evaluation Efficiency of Different Isolate of Actinomycetes for Control of Cucumber Seedling Damping-off Disease Caused by Rhizoctonia solani (Khun)

Fayyadh, M.A. and L.K. Awad. 2021. Evaluation Efficiency of Different Isolate of Actinomycetes for Control of Cucumber Seedling Damping-off Disease Caused by Rhizoctonia solani (Khun). Arab Journal of Plant Protection, 39(4): 281-288. https://doi.org/10.22268/AJPP-39.4.281288 This study was conducted in Plant Protection Department, College of Agriculture, University of Basrah during the period 2017-2018 aimed to isolate and identify Actinomycetes from different environmental sources and evaluate their efficiency to control cucumber damping off disease caused by Rhizoctonia solani. 28 isolates of Actinomycetes were isolated from different sources from the Basrah region. All such isolates were gram positive, amylase and catalase positive and they had branched hyphae. Molecular identification following amplification of 16sRNA confirmed that Actinomycetes isolate No 6 isolated from soil had a similarity of 99% with Streptomyces griseus, whereas the isolate No 66 isolated from date palm roots had a similarity of 99% with Brevibacterium celere. The nucleotide sequence of the two isolates has been deposited at NCBI with Genbank accession number LC501385.1 for S. griseus and LC501386.1 for B. celere. The dual culture technique showed that Actinomycetes isolates S. griseus and B. celere had high antagonistic activity against Rhizoctonia solani, which produced inhibition zones of 7 and 15 mm in dimeter, respectively. On the other hand, volatile compoundsreleased from S. griseus and B. celere inhibited the growth of R. solani by 68 and 81.5%, respectively. Pot experiment showed that all actinomycetes isolates significantly reduced cucumber seedling damping–off incidence caused by R. solani. Keywords: Actinomycetes, Rhizoctonia solani, Cucumber, Biological Control

Delving into defence: identifying the Pseudomonas protegens Pf-5 gene suite involved in defence against secreted products of fungal, oomycete and bacterial rhizosphere competitors

Competitive behaviours of plant growth promoting rhizobacteria (PGPR) are integral to their ability to colonize and persist on plant roots and outcompete phytopathogenic fungi, oomycetes and bacteria. PGPR engage in a range of antagonistic behaviours that have been studied in detail, such as the production and secretion of compounds inhibitory to other microbes. In contrast, their defensive activities that enable them to tolerate exposure to inhibitory compounds produced by their neighbours are less well understood. In this study, the genes involved in the Pseudomonas protegens Pf-5 response to metabolites from eight diverse rhizosphere competitor organisms, Fusarium oxysporum, Rhizoctonia solani, Gaeumannomyces graminis var. tritici, Pythium spinosum, Bacillus subtilis QST713, Pseudomonas sp. Q2-87, Streptomyces griseus and Streptomyces bikiniensis subspecies bikiniensi, were examined. Proximity induced excreted metabolite responses were confirmed for Pf-5 with all partner organisms through HPLC before culturing a dense Pf-5 transposon mutant library adjacent to each of these microbes. This was followed by transposon-directed insertion site sequencing (TraDIS), which identified genes that influence Pf-5 fitness during these competitive interactions. A set of 148 genes was identified that were associated with increased fitness during competition, including cell surface modification, electron transport, nucleotide metabolism, as well as regulatory genes. In addition, 51 genes were identified for which loss of function resulted in fitness gains during competition. These included genes involved in flagella biosynthesis and cell division. Considerable overlap was observed in the set of genes observed to provide a fitness benefit during competition with all eight test organisms, indicating commonalities in the competitive response to phylogenetically diverse micro-organisms and providing new insight into competitive processes likely to take place in the rhizosphere.

Influence of environmental conditions on plants in different climatic zones

Due to global shifts in climate, studies in contrasting conditions of two natural and climatic zones are of particular interest: (1) subzone of mixed and broad-leaved forests, (2) south-steppe subzone. In the period 2019-2020, 308 plant species from 56 families were surveyed. Phytopathogens damage plants, and therefore increase the loss of quality of plant materials. The frequency of occurrence of mycoses in autumn is 2-14 times higher than in spring-summer observations. The activity of phytopathogenic fungi of the genera of Fusarium (the causative agent of fusarium), Puccinia (rust), Phoma (phomosis), Rhizoctonia (scab), Verticillium (tracheomycotic or vascular wilting) increases. Differences in dominant micromycetes from the point of view of geography were determined: zone 1 (forest) - Alternaria spp., Chaetomium spp., Fusarium spp., F. avenaceum (Fr.) Sacc., (Mart.) Sacc., Heterosporium iridis (Fautrey & Roum.) JE Jacques, Phoma spp., Stemphylium spp., Verticillium spp.; zone 2 (steppe) – Alternaria spp., Botrytis spp., Cladosporium spp., Fusarium avenaceum, Fusarium spp., Peronospora spp., Phoma spp., Pullularia spp., Septoria spp. Screening of pesticides (biological fungicides) showed the effectiveness of preparations based on Pseudomonas fluorescens, Bacillus subtilis or Streptomyces griseus in limiting the growth of the mycelium of phytopathogenic fungi.

Spinning sugars in antigen biosynthesis: a direct study of the Coxiella burnetii and Streptomyces griseus TDP-sugar epimerases

The sugars streptose and dihydrohydroxystreptose (DHHS) are unique to the bacteria Streptomyces griseus and Coxiella burnetii respectively. Streptose forms the central moiety of the antibiotic streptomycin, whilst DHHS is found in the O-antigen of the zoonotic pathogen C. burnetii. Biosynthesis of these sugars has been proposed to follow a similar path to that of TDP-rhamnose, catalysed by the enzymes RmlA/RmlB/RmlC/RmlD. Streptose and DHHS biosynthesis unusually require a ring contraction step that might be performed by the orthologues of RmlC or RmlD. Genome sequencing of S. griseus and C. burnetii proposed the StrM and CBU1838 proteins respectively as RmlC orthologues. Here, we demonstrate through both coupled and direct observation studies that both enzymes can perform the RmlC 3'',5'' double epimerisation activity; and that this activity supports TDP-rhamnose biosynthesis in vivo. We demonstrate that proton exchange is faster at the 3'' position than the 5'' position, in contrast to a previously studied orthologue. We solved the crystal structures of CBU1838 and StrM in complex with TDP and show that they form an active site highly similar to previously characterised enzymes. These results further support the hypothesis that streptose and DHHS are biosynthesised using the TDP pathway and are consistent with the ring contraction step being performed on a double epimerised substrate, most likely by the RmlD paralogue. This work will support the determination of the full pathways for streptose and DHHS biosynthesis.

Selection of the Optimal L-asparaginase II Against Acute Lymphoblastic Leukemia: An In Silico Approach

Background L-asparaginase II (asnB), a periplasmic protein commercially extracted from E coli and Erwinia, is often used to treat acute lymphoblastic leukemia. L-asparaginase is an enzyme that converts L-asparagine to aspartic acid and ammonia. Cancer cells are dependent on asparagine from other sources for growth, and when these cells are deprived of asparagine by the action of the enzyme, the cancer cells selectively die. Objective Questions remain as to whether asnB from E coli and Erwinia is the best asparaginase as they have many side effects. asnBs with the lowest Michaelis constant (Km; most potent) and lowest immunogenicity are considered the most optimal enzymes. In this paper, we have attempted the development of a method to screen for optimal enzymes that are better than commercially available enzymes. Methods In this paper, the asnB sequence of E coli was used to search for homologous proteins in different bacterial and archaeal phyla, and a maximum likelihood phylogenetic tree was constructed. The sequences that are most distant from E coli and Erwinia were considered the best candidates in terms of immunogenicity and were chosen for further processing. The structures of these proteins were built by homology modeling, and asparagine was docked with these proteins to calculate the binding energy. Results asnBs from Streptomyces griseus, Streptomyces venezuelae, and Streptomyces collinus were found to have the highest binding energy (–5.3 kcal/mol, –5.2 kcal/mol, and –5.3 kcal/mol, respectively; higher than the E coli and Erwinia asnBs) and were predicted to have the lowest Kms, as we found that there is an inverse relationship between binding energy and Km. Besides predicting the most optimal asparaginase, this technique can also be used to predict the most optimal enzymes where the substrate is known and the structure of one of the homologs is solved. Conclusions We have devised an in silico method to predict the enzyme kinetics from a sequence of an enzyme along with being able to screen for optimal alternative asnBs against acute lymphoblastic leukemia.

Isolation of antibiotics producing bacteria from marine soil and comparative analysis of same with commercially available drugs

The isolation of antibiotic producing bacteria from marine soil and comparative analysis of same with ciprofloxacin and amoxicillin against staphylococcus aureus and Escherichia coli was carried out in a Microbiology Laboratory of Chukwuemeka Odumegwu Ojukwu University, Uli. This was done to isolate antibiotic producing bacteria and compare same with existing commercially available antibiotics with a view to using marine soil in the treatment of common bacterial infections. Soil samples were collected from Bonny Island Sea, Port Harcourt. One gram of mixed soil sample was serially diluted and spread-plated on nutrient agar plates. The representative isolates obtained were sub-cultured to get a pure culture. Morphological, biochemical, physiological characteristics of the bacteria were analyzed. Agar well diffusion was carried out. One isolate had a substantial antibacterial activity with 3.5mm zone of inhibition against two test bacteria used in the preliminary screening. The isolate was marked as Streptomyces (STR I) and was identified as Streptomyces griseus while other isolates did not show any antibacterial activity. Ciprofloxacin showed the highest antibacterial activity to both Staphylococcus aureus and Escherichia coli of 3.7mm and 4.0mm respectively while Amoxicillin showed antibacterial activity of 3.5mm and 2.7mm respectively. This reveals that antibiotic producing bacteria from marine soil are also effective in antimicrobial activity and could be used for antimicrobial chemotherapy.

Streptomyces griseus KJ623766: A Natural Producer of Two Anthracycline Cytotoxic Metabolites β- and γ-Rhodomycinone

Background: This study aimed to produce, purify, structurally elucidate, and explore the biological activities of metabolites produced by Streptomyces (S.) griseus isolate KJ623766, a recovered soil bacterium previously screened in our lab that showed promising cytotoxic activities against various cancer cell lines. Methods: Production of cytotoxic metabolites from S. griseus isolate KJ623766 was carried out in a 14L laboratory fermenter under specified optimum conditions. Using a 3-(4,5-dimethylthazol-2-yl)-2,5-diphenyl tetrazolium-bromide assay, the cytotoxic activity of the ethyl acetate extract against Caco2 and Hela cancer cell lines was determined. Bioassay-guided fractionation of the ethyl acetate extract using different chromatographic techniques was used for cytotoxic metabolite purification. Chemical structures of the purified metabolites were identified using mass, 1D, and 2D NMR spectroscopic analysis. Results: Bioassay-guided fractionation of the ethyl acetate extract led to the purification of two cytotoxic metabolites, R1 and R2, of reproducible amounts of 5 and 1.5 mg/L, respectively. The structures of R1 and R2 metabolites were identified as β- and γ-rhodomycinone with CD50 of 6.3, 9.45, 64.8 and 9.11, 9.35, 67.3 µg/mL against Caco2, Hela and Vero cell lines, respectively. Values were comparable to those of the positive control doxorubicin. Conclusions: This is the first report about the production of β- and γ-rhodomycinone, two important scaffolds for synthesis of anticancer drugs, from S. griseus.