Marine Sediment Recovered Salinispora sp. Inhibits the Growth of Emerging Bacterial Pathogens and other Multi-Drug-Resistant Bacteria.

Marine obligate actinobacteria produce a wide variety of secondary metabolites with biological activity, notably those with antibiotic activity urgently needed against multi-drug-resistant bacteria. Seventy-five marine actinobacteria were isolated from a marine sediment sample collected in Punta Arena de La Ventana, Baja California Sur, Mexico. The 16S rRNA gene identification, Multi Locus Sequence Analysis, and the marine salt requirement for growth assigned seventy-one isolates as members of the genus Salinispora, grouped apart but related to the main Salinispora arenicola species clade. The ability of salinisporae to inhibit bacterial growth of Staphylococcus epidermidis, Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacer baumannii, Pseudomonas aeruginosa, and Enterobacter spp. was evaluated by cross-streaking plate and supernatant inhibition tests. Ten supernatants inhibited the growth of eight strains of S. epidermidis from patients suffering from ocular infections, two out of the eight showed growth inhibition on ten S. epidermidis strains from prosthetic joint infections. Also, it inhibited the growth of the remaining six multi-drug-resistant bacteria tested. These results showed that some Salinispora strains could produce antibacterial compounds to combat bacteria of clinical importance and prove that studying different geographical sites uncovers untapped microorganisms with metabolic potential.

Induction of innate immune response in whiteleg shrimp (Litopenaeus vannamei) embryos.

The immune response of commercially relevant marine invertebrates has been extensively studied, in search of new disease-control strategies. Immune training is considered a novel approach that could help improve resistance to different pathogens. Here, we stimulated the white shrimp (Litopenaeus vannamei) during embryo development by exposure to heat-killed bacteria and evaluated their effect on hatching, larval development, and the expression of immune-related genes. In addition, we evaluated its impact on the response of shrimp nauplii during a challenge with Vibrio parahaemolyticus. We observed that the percentage of hatching and the resistance to bacterial infection increased due to the treatment of embryos with heat-killed cells of Vibrio and Bacillus. Apparently different stimuli could generate a differential pattern of gene expression, e.g., Vibrio induced a strong effector immune response whereas Bacillus elicited a protective immune profile. In addition, each response was triggered by molecular patterns detected in the environment. The results obtained in this study provide new insights for immune training to improve shrimp farming.

Administration of Probiotics Improves the Brine Shrimp Production and Prevents Detrimental Effects of Pathogenic Vibrio Species.

In this study, we evaluated a consortium of probiotic bacteria as an environmentally-friendly strategy for controlling pathogenic Vibrio species during the brine shrimp incubation period. Probiotic strains were initially selected on basis of (i) their ability to colonize the cyst surfaces, (ii) their absence of cross-inhibitory effects, and (iii) no detrimental effect on cyst hatching. The cysts and nauplius surfaces were immediately colonized after the application of selected probiotic strains, without detrimental effects on survival. Ten probiotic strains were mixed at similar proportions (probiotic consortium) and evaluated at different concentrations into brine shrimp cultures during incubation and early stages of development. Subsequently, these cultures were challenged with Vibrio parahaemolyticus and Vibrio harveyi. The probiotic consortium was effective to reduce the abundance of pathogenic Vibrio species and to prevent the mortality during Vibrio challenges; however, its effect was concentration-dependent and was successful at a starting concentration of 1.8 × 106 CFU/ml. Our results suggest that this probiotic consortium offers an alternative to antimicrobial agents routinely used to reduce the incidence and prevalence of pathogenic Vibrio species in brine shrimp production.

Genome sequence analysis of the Vibrio parahaemolyticus lytic bacteriophage VPMS1.

VPMS1 is a Vibrio parahaemolyticus lytic phage isolated from a marine clam. The 42.3-kb genome was predicted to encode 53 proteins. Comparison of the VPMS1 DNA genome with known phage genomes revealed no similarity; hence, it represents a new VP phage, organized into three differently oriented modules. The module for packaging covers 12 % of the genome, the module for structure covers 31 %, and the module for replication and regulation covers 48 %. The G + C content was 44.67 %. The coding region corresponds to 91 % of the genome, and 9 % apparently does not encode any protein. Thirty genes, constituting 57 % of the genome, had significant similarity to some reported proteins in the protein database; 23 genes, constituting 43 % of the genome, showed no significant homology to any reported protein, and these could be new proteins whose hypothetical functions can be deduced from their position in the genome.