The Potential of Phylogenetically Diverse Culturable Actinobacteria from Litopenaeus vannamei Pond Sediment as Extracellular Proteolytic and Lipolytic Enzyme Producers.

Enzymes are catalysts that can increase the reaction time of a biochemical process. Hydrolytic enzymes have a pivotal role in degrading organic waste in both terrestrial and aquatic environments. The aims of this study were (1) to investigate the ability of actinobacteria isolated from Litopenaeus vannamei pond sediment to produce proteolytic and lipolytic enzymes, (2) to identify promising candidates using 16S rRNA gene amplification, and (3) to construct a phylogenetic tree based on the 16S rRNA genes. A skim milk agar medium was used in the preliminary experiment of the proteolytic assay, and a Tween 20/80 medium was used in the lipolytic assay. Fifteen and 20 (out of 40) actinobacterial isolates showed great potential for proteolytic and lipolytic activities, respectively. Furthermore, four actinobacteria isolates produced both enzyme types with proteolytic and lipolytic index scores of 1-6.5. The most promising candidates were SA 2.2 (IM8), SC 2.1 (IM6), SD 1.5 (IM6) and SE 1.1 (IM8). BLAST homology results showed a high similarity between the actinobacteria isolates and Streptomyces verucosisporus, S. mangrovicola, S. barkulensis and Nocardiopsis lucentensis, respectively. Therefore, actinobacteria from Litopenaeus vannamei pond sediment are high-potential proteolytic and lipolytic enzyme producers.

Bioactivity of compounds secreted by symbiont bacteria of Nudibranchs from Indonesia.

The aims of this work are to isolate bacterial symbionts from nudibranchs and subsequently to determine anti-Methicillin resistant Staphylococcus aureus (MRSA), cytotoxicity and anti-Herpes simplex virus type 1 (HSV-1) activities of bio compounds. A total of 15 species of nudibranchs were collected from Karimunjawa and five species from Bali, respectively. A total of 245 bacteria isolates were obtained. The anti-MRSA activity screening activity indicated two active bacteria. Ethyl acetate extracts from supernatants, indicating extracelullar compounds, showed an inhibition zone against MRSA at concentrations of 500-1,000 µg/ml. DNA sequence analysis showed that the strain KJB-07 from Phyllidia coelestis was closely related to Pseudoalteromonas rubra, whereas the strain NP31-01 isolated from Phyllidia varicosa was closely related to Virgibacillus salarius. The extract of Pseudoalteromonas rubra was cytotoxic to Vero cells at a concentration of 75 µg/ml. The extract of V. salarius presented no cytotoxicity at concentrations of 5-1,000 µg/ml. No anti HSV-1 was observed for both isolated bacteria. This is the first study describing research on anti-MRSA, cytotoxicity and anti HSV-1 activity of bacterial symbionts from the viscera of nudibranch. Compounds produced by Pseudoalteromonas rubra and V. salarius, had potential anti-MRSA activity. However, only extracts from Pseudoalteromonas rubra showed cytotoxic effects on Vero cells. Three compounds were identified by LC/MS after purification from culture supernatant.

Tunicate-associated bacteria show a great potential for the discovery of antimicrobial compounds.

Tunicates (Ascidians, sea squirts) are marine protochordates, which live sedentary or sessile in colonial or solitary forms. These invertebrates have to protect themselves against predators and invaders. A most successful strategy, to not being eaten by predators and prevent pathogenic microorganisms to settle, is the usage of chemical molecules for defence. To accomplish this, tunicates take advantage of the specialized metabolites produced by the bacteria associated with them. Therefore, the microbiome of the tunicates can be regarded as a promising bioresource for bacterial strains producing compounds with antibacterial activity. The aim of this study was to test this hypothesis by (i) isolation of tunicate-associated bacteria, (ii) analysis of the antibacterial activities of these strains, and (iii) purification and structure elucidation of an active compound derived from this bioresource. In total, 435 bacterial strains were isolated and thereof 71 (16%) showed antibacterial activity against multidrug resistant (MDR) bacteria. Therefrom, the ethyl acetate crude extracts from liquid fermentations of 25 strains showed activity against MDR Extended-Spectrum Beta-Lactamase (MDR-ESBL) Escherichia coli, MDR Bacillus cereus, Micrococcus luteus, and Bacillus megaterium. Phenotypic analysis based on 16S rDNA sequencing revealed the active strains belonging to different genera and phyla, like Bacillus, Pantoea, Pseudoalteromonas, Salinicola, Streptomyces, Vibrio and Virgibacillus. To obtain first insights into the molecules responsible for the antibacterial activities observed, strain Pseudoalteromonas rubra TKJD 22 was selected for large-scale fermentation and the active compound was isolated. This allowed the purification and structure elucidation of isatin, a compound known for its strong biological effects, thereunder inhibition of Gram-positive and Gram-negative pathogens.