Fourteen seaweeds collected from the intertidal zone of Southwest coast of India were tested against ten human pathogen bacteria and one human pathogen fungus using the well diffusion test in the casitone agar medium. The species used in the present study include five Chlorophyta (Bryopsis plumosa, Ulva fasciata, Acrosiphonia orientalis, Chaetomorpha antennina, Grateloupia filicina), five Rhodophyta (Hypnea pannosa, Gracilaria corticata, Centroceras clavulatum, Portieria hornemannii, Cheilosporum spectabile) and four Phaeophyta (Padina tetrastromatica, Sargassum wightii, Stocheospermum marginatum, Chnoospora bicanaliculata). Of these, seven species were determined to be highly bioactive and screened on the multiresistant pathogens. We found that drying process has eliminated the active principles in the seaweeds. In the present study, methanol:toluene (3:1) was found to be the best solvent for extracting the antimicrobial principles from fresh algae. However, the ethanolic extract showed no antibacterial activity. Acrosiphonia orientalis showed activity against 70% of the tested organisms. Stocheospermum marginatum was the only seaweed that showed activity against Klebsiella pneumoniae. The extract from Gracilaria corticata was highly active against Proteus mirabilis, a Gram negative pathogenic bacterium. The present findings revealed that the tested seaweeds were highly active against Gram negative bacteria than Gram positive bacteria. The antimicrobial principle from seaweed was found to be a lipophilic compound. The compound was stable over a wide range of temperature (30-60 °C). The active principles of highly active seaweeds Acrosiphonia orientalis and Stocheospermum marginatum were bactericidal.

Taking into consideration the needs of greener bioprocesses and novel enhancers for synthesis using microbial processes, biosurfactants, and/or biosurfactant producing microbes are emerging as an alternate source for the rapid synthesis of nanoparticles. A microemulsion technique using an oil-water-surfactant mixture was shown to be a promising approach for nanoparticle synthesis. Biosurfactants are natural surfactants derived from microbial origin composed mostly of sugar and fatty acid moieties, they have higher biodegradability, lower toxicity, and excellent biological activities. The biosurfactant mediated process and microbial synthesis of nanoparticles are now emerging as clean, nontoxic, and environmentally acceptable "green chemistry" procedures. The biosurfactant-mediated synthesis is superior to the methods of bacterial- or fungal-mediated nanoparticle synthesis, since biosurfactants reduce the formation of aggregates due to the electrostatic forces of attraction and facilitate a uniform morphology of the nanoparticles. In this review, we highlight the biosurfactant mediated synthesis of nanoparticles with relevant details including a greener bioprocess, sources of biosurfactants, and biological synthesized nanoparticles based on the available literature and laboratory findings.

No abstract

Vibrios are prominently opportunistic, but they may act as primary and secondary pathogenic invaders of shrimps in farms worldwide. However, little is known about the virulence of diverse vibrios harbored in shrimp farms. The isolation of secondary/opportunistic Vibrio pathogens was carried out from the shrimp farms located in peninsular India, reported to have mass mortalities because of White‐spot syndrome virus and shell disease outbreaks. The isolates were identified and grouped into six species including luminescent Vibrio harveyi, Vibrio alginolyticus, Vibrio vulnificus, Vibrio fischeri, Vibrio parahaemolyticus, and Photobacterium damsela. To make a detailed study on their virulence, the isolates were screened in vitro for the production of extracellular factors. In the present study, 68.9% of the shrimp Vibrio isolates were found to be positive for both phospholipase and hemolysin production. The results showed that various factors including hydrophobicity, presence of capsule, and production of extracellular enzymes such as lipase, protease, phospholipase, and hemolysin were responsible for pathogenesis. Using the bacterial adherence to hydrocarbons, most of the strains were classified as highly hydrophobic. In vivo challenge experiments using the Vibrio species and the extracellular products demonstrated the pathogenicity of vibrios. In the present study, we established the shrimp farm water isolates V. vulnificus, V. fischeri, and P. damsela as moderately opportunistic shrimp pathogens.

No abstract