bacillomycin-d and mycosubtiline

In the current study, the biocontrol potential of a novel strain Bacillus sp. PPM3 isolated from marine sediment from the Red Sea in Hurghada, Egypt is recognized. This novel strain was selected out of 32 isolates based on its ability to suppress the growth of four plant pathogenic fungi: Aspergillus flavus, Fusarium graminearum, Mucor sp. and Alternaria sp. The new marine strain was identified and characterized by phenotypic and molecular approaches. The culture filtrate of Bacillus sp. PPM3 suppressed the growth and spore germination of all tested fungi in vitro with the highest value of inhibition reported for Mucor sp. (97.5%). The antifungal effect of the culture filtrate from the strain PPM3 was due to production of highly stable secondary metabolites resistant to extreme pH, temperature and enzymatic treatments. A PCR analysis confirmed the expression of genes involved in the synthesis of antifungal lipopeptides: iturin, bacillomycin D, mycosubtilin and surfactin. In a greenhouse experiment strain PPM3 effectively reduced disease incidence of F. graminearum in maize plants and displayed additional plant growth stimulating effect. The results show that novel marine strain PPM3 could have a potential in commercial application as biocontrol agent for treatment of various plant diseases caused by soil-borne and postharvest pathogenic fungi.

Topics: Alternaria; Antifungal Agents; Antimicrobial Cationic Peptides; Aspergillus flavus; Bacillus; Biological Control Agents; DNA, Bacterial; Egypt; Fungi; Fusarium; Geologic Sediments; Hydrogen-Ion Concentration; Indian Ocean; Lipopeptides; Lipoproteins; Mucor; Peptides; Peptides, Cyclic; Plant Development; Plant Diseases; RNA, Ribosomal, 16S; Secondary Metabolism; Seedlings; Species Specificity; Spores, Fungal; Temperature; Zea mays

Marine biofilms are a virtually untapped source of bioactive molecules that may find application as novel antifoulants in the marine paint industry. This study aimed at determining the potential of marine biofilm bacteria to produce novel biomolecules with potential application as natural antifoulants. Nine representative strains were isolated from a range of surfaces and were grown in YEB medium and harvested during the late exponential growth phase. Bacterial biomass and spent culture medium were extracted with ethanol and ethyl acetate, respectively. Extracts were assayed for their antifouling activity using two tests: (1) antimicrobial well diffusion test against a common fouling bacterium, Halomonas marina, and (2) anti-crustacean activity test using Artemia salina. Our results showed that none of the ethanolic extracts (bacterial biomass) were active in either test. In contrast, most of the organic extracts had antimicrobial activity (88%) and were toxic towards A. salina (67%). Sequencing of full 16 S ribosomal DNA analysis showed that the isolates were related to Bacillus mojavensis and Bacillus firmus. Matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF-MS) profiling of ethyl acetate extracts of culture supernatants showed that these species produce the bioactive lipopeptides surfactin A, mycosubtilin and bacillomycin D.

Topics: Animals; Anti-Bacterial Agents; Antimicrobial Cationic Peptides; Artemia; Bacillus; Biofilms; Calcium Carbonate; Halomonas; Hydrocharitaceae; Lipopeptides; Lipoproteins; Molecular Sequence Data; Peptides; Peptides, Cyclic; Phylogeny; Plant Leaves; Seawater; Sequence Analysis, DNA; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization

Bacillus subtilis AU195 produces bacillomycin D, a cyclic lipopeptide that is an inhibitor of the aflatoxin producing fungus Aspergillus flavus. Sequence analysis of the bacillomycin D operon revealed four ORFs with the structural organization of the peptide synthetases. Disruption of ORF 2, which links the amino acid moiety to the b-amino fatty acid, resulted in the loss of antifungal activity. By comparing the sequence of bacillomycin D, iturin A and mycosubtilin operons, our results showed that intergenic module replacement have occurred between B. subtilis lipopeptide synthetases including the iturin family and the plipastatin and fengycin family.

Topics: Antifungal Agents; Antimicrobial Cationic Peptides; Bacillus subtilis; Cloning, Molecular; DNA, Bacterial; Gene Order; Ligases; Lipoproteins; Microbial Sensitivity Tests; Molecular Sequence Data; Mutagenesis, Insertional; Open Reading Frames; Operon; Peptide Synthases; Peptides; Peptides, Cyclic; Phylogeny; Recombination, Genetic; Sequence Analysis, DNA; Sequence Homology

Iturinic antibiotics, produced by different strains of Bacillus subtilis, contain long-chain beta-amino acids (beta-AA). The regulation of the synthesis of fatty acids (FA) and beta-AA was studied by modifying the culture medium. Addition of possible precursors, branched-chain alpha-amino acids, to the medium affected the FA and beta-AA compositions. According to this, the B. subtilis strains can be divided into two groups. The first contains the producers of mycosubtilin and bacillomycin F which synthesize a high level of iso C16 chains; the second contains the producers of bacillomycin D, bacillomycin L and iturin which synthesize a high level of n carbon chains. The incorporation of radioactive sodium acetate into FA and beta-AA showed rapid FA synthesis followed by a second synthetic step. Although the detailed mechanism has not yet been elucidated, this second step, corresponding to the beta-AA synthesis, seemed to be a key step in determining the alkyl chain of beta-AA.

Topics: Amino Acids; Amino Acids, Branched-Chain; Anti-Bacterial Agents; Antifungal Agents; Antimicrobial Cationic Peptides; Bacillus subtilis; Fatty Acids; Lipoproteins; Peptides; Peptides, Cyclic