Antimicrobial activity of bacteria isolated from tissue of the coral Palythoa caribaeorum (Zoantharia: Sphenopidae) from Paraíba, Brazil coastal reefs / Actividad antimicrobiana de bacterias aisladas del tejido del coral Palythoa caribaeorum (Zoantharia: Sphenopidae) de los arrecifes costeros de Paraíba, Brasil

Abstract Introduction: The coral-associated bacteria with antimicrobial activity may be important to promote the health of their host through various interactions, and may be explored as a source of new bioactive compounds. Objective: To analyze the antimicrobial activity of bacteria associated with the zoanthid Palythoa caribaeorum from the coral reefs of Carapibus, Paraiba state, Brazil. Methods: The phylogenetic analysis of the bacteria was conducted based on partial sequences of the 16S rRNA gene using molecular and bioinformatics tools. The antimicrobial activity of the 49 isolates was tested against four bacterial strains and one yeast strain: Bacillus cereus (CCT0198), Escherichia coli (ATCC 25922), Staphylococcus aureus (ATCC 25923), Pseudomonas aeruginosa and Candida albicans (ATCC 10231). The antibiosis and antibiogram assays were conducted and the Minimal Inhibitory Concentration (MIC) was determined by the microdilution method. Results: The bacterial isolates belonged to Firmicutes phylum (84 % of the isolates) and the Proteobacteria phylum (16 % of the isolates). Among the 49 isolates five genera were found, with the Bacillus genus being the most abundant (82 % of the isolates), followed by Vibrio (10 %), Pseudomonas (4 %), Staphylococcus (2 %) and Alteromonas (2 %). Antibiosis test revealed that 16 isolates (33 %) showed antimicrobial activity against one or more of five tested reference strains. The highest number of antagonistic bacteria were found in the Bacillus genus (12 isolates), followed by Vibrio (three isolates) and Pseudomonas (one isolate) genera. The B. subtilis NC8 was the only isolate that inhibited all tested strains in the antibiosis assay. However, antibiogram test with post-culture cell-free supernatant of NC8 isolate showed the inhibition of only B. cereus, S. aureus and C. albicans, and the lyophilized and dialyzed material of this isolate inhibited only B. cereus. The lyophilized material showed bacteriostatic activity against B. cereus, with a MIC value of 125 μg/μl, and in the cytotoxicity assay, the hemolysis value was of 4.8 %, indicating its low cytotoxicity. Conclusions: The results show the antimicrobial potential of some bacterial isolates associated with the P. caribaeourum tissue, especially those belonged to Bacillus genus.

Resumen Introducción: La actividad antimicrobiana realizada por las bacterias asociadas con los corales, además de promover la salud de su huésped, representa una fuente para obtener nuevos compuestos bioactivos. Objetivo: Analizar la actividad antimicrobiana de las bacterias asociadas con el zoantario Palythoa caribaeorum de los arrecifes de Carapibus, Paraíba, Brasil. Metodología: El análisis filogenético de la bacterias se realizó con base en secuencias parciales del gen RNAr 16S utilizando herramientas moleculares y de bioinformática. La actividad antimicrobiana de las cepas se probó contra cuatro cepas bacterianas y una cepa de levadura: Bacillus cereus (CCT0198), Escherichia coli (ATCC 25922), Staphylococcus aureus (ATCC 25923), Pseudomonas aeruginosa y Candida albicans (ATCC 10231), utilizando ensayos antibiosis y antibiograma, y la concentración inhibitoria mínima (CIM) que se determinó por el método de microdilución. Resultados: Las cepas bacterianas pertenecían a Firmicutes (84 %) y Gammaproteobacteria (16 %). Entre 49 cepas se encontraron cinco géneros de bacterias: Bacillus, Vibrio, Pseudomonas, Staphylococcus y Alteromonas. Un total de 19 cepas exhibieron actividad antimicrobiana, siendo el género Bacillus el responsable del mayor número de bacterias antagonistas, con 12 cepas positivas en el ensayo de antibiosis y cuatro en la prueba de antibiograma. El mayor número de bacterias antagonistas se encontró en Bacillus (12 aislamientos), seguido por Vibrio (tres aislamientos) y Pseudomonas (un aisladmiento). El NC8, clasificado como Bacillus subtilis, inhibió todas las cepas estándar en el ensayo de antibiosis y las cepas de B. cereus, S. aureus y C. albicans en la prueba de antibiograma. El material liofilizado del B. subtilis NC8 mostró acción bacteriostática contra B. cereus, con un valor de CIM de 125 μg/μl. En la prueba de citotoxicidad, el grado de hemólisis fue del 4.8 % para el material liofilizado a las concentraciones probadas, lo que indica su baja citotoxicidad. Conclusión: Los resultados muestran el potencial antimicrobiano de algunos aislamientos bacterianos asociados al P. caribaeourum, especialmente los pertenecientes al género Bacillus.

Anti-staphylococcal and antifungal substances produced by endospore-forming bacilli.

Some bacteria and fungi are related to deterioration and also transmission of foodborne diseases, emphasizing the need to search new substances that may act in the treatment and prevention of the illnesses transmitted by food. Strains from genus Bacillus produce a variety of substances with inhibitory activity that range from antibiotics to bacteriocins. In this work, three strains, identified as B. pasteurii (Pes1) and B. insolitus (Mam2 and Ame3) presented inhibitory action against staphylococcal strains isolated from food. Out of the 33 strains tested, 31 (94.0%) were inhibited by at least one of three main Bacillus producer strains, being most of them inhibited by strain Pes1, that also was able to inhibit filamentous fungi related to food spoilage. The antimicrobial substances produced by Pes1, Mam2 and Ame3 showed to be resistant to proteolytic enzymes, suggesting these substances have not an active proteinaceous compound, as typical bacteriocins. New studies are being performed to extract and characterize these antimicrobial agents to evaluate their potential application in biological control of microorganisms related to spoilage food and foodborne diseases.

Isolation of Antimicrobial Substances from Hericium erinaceum

Mycelium of Hericium erinaceum isolate KU-1 was cultured in liquid medium (HL medium) and solid medium (Ko medium) at pH 4.0 in 28degrees C. 1.0% glucose or fructose was the most favorable carbon source, and 0.2% amonium acetate or NaNO3 was an exellent nitrogen source for mycelial growth as well as production of antimicrobial substances. The mixture of saw dust 70% with rice bran 30% (SR medium) was the substrate for formation of sporophores. The active substrates in extracts from mycelium, culture filtrate and fruiting body were separated by TLC. The solvent for TLC was EtOAc: Chloroform: MeOH (10 : 5 : 10). Phenol-like substances appeared at Rf 0.5~0.9, and fatty acid-like substances appeared at Rf 0.1~0.2. The purified materials from the extracts showed antimicrobial effects to Escherichia coli, Bacillus subtilis, Staphylococcus aureus, Aspergillus niger, Candida albicans and Microsporum gypseum. The S. aureus was the most inhibited. Minimal inhibitory concentration (MIC) of purified white powder and the Hercenone derivatives against S. aureus were 5.65microg/ml and 1.85microg/ml, respectively.

Identification of Antagonistic Strain P-13 and the Preliminary Studies on Its Antimicrobial Substances Against Bacterial Spot Diseases of Muskmelon / 微生物学通报

An actinomycete strain P-13, with antimicrobial activity against muskmelon bacterial spot pathogens, was isolated from the muskmelon rhizosphere soil samples in Xinjiang. The strain P-13 was identified as Streptomyces rochei based on morphological, physiological characteristics and 16S rRNA sequence analysis. The agar diffusion bioassay showed that the diameter of inhibition zone against Acidovorax avenae subsp. citrull BFB and Pseudomonas syringae pv. Lachrymans P4 was above 19 mm and 17 mm, respectively. The antimicrobial substances obtained from strain P-13 were demonstrated to be alkaline and water-soluble compounds according to paper chromatogram analysis and exocellular metabolites. Furthermore, it was stable to be treated by 100?C for 10 min, pH 6 for 6 h, or ultraviolet treatment for 7 h. Moreover, it was insoluble in organic solvents, such as petroleum benzine, diethyl ether, and acetic ether.