Novel antimicrobial activity of a dichloromethane extract obtained from red seaweed Ceramium rubrum (Hudson) (Rhodophyta: Florideophyceae) against Yersinia ruckeri and Saprolegnia parasitica, agents that cause diseases in salmonids

Background Enteric red mouth disease and Saprolegniasis, which are caused by the bacteria Yersinia ruckeri and the oomycete Saprolegnia parasitica, respectively, are important illnesses that affect salmonid farming. Sanitary problems in farms are addressed by the prevention of disease outbreaks or by the treatment of diseases with chemicals. Environmental and governmental restrictions, toxicity and high treatment costs limit the use of drugs. Marine organisms, such as algae, sponges and corals, have developed an antimicrobial defense strategy based on the production of bioactive metabolites. Among these organisms, seaweeds offer a particularly rich source of potential new drugs. Hence, many pharmacologically active substances have been isolated from seaweeds. In the Ceramium genus, Ceramium rubrum has been emphasized by several authors for its antimicrobial properties. Based on this background, the present study focused on the antimicrobial activity of a lipophilic extract of C. rubrum on Y. ruckeri and S. parasitica. Results The alga, collected from the Pacific coast of Chile, underwent an ethanol extraction, and the concentrated extract was partitioned between water and dichloromethane. From the dichloromethane extract, fatty acids, fatty acid esters, one hydrocarbon and phytol were identified by Gas Chromatography-Mass Spectrometry (GC/MS) analysis. The antimicrobial study showed that the whole extract was more active than the individual components, which suggests a strong synergistic effect among the components. Conclusions These results may constitute a basis for promising future applied research that could investigate the use of C. rubrum seaweed as a source of antimicrobial compounds against fish pathogens.

Characterization of protease from Alcaligens faecalis and its antibacterial activity on fish pathogens.

Alcaligens faecalis AU01 isolated from seafood industry effluent produced an alkaline protease. The optimum culture conditions for growth as well as enzyme production were 37oC and pH 8. The partially purified protease had specific activity of 9.66 with 17.77% recovery with the molecular weight of 33 kDa and it was active between 30-70oC and optimum being at 55oC and pH 9. The enzyme retains more than 85% activity at 70oC and 78% even at pH 10.The enzyme inhibited the growth of fish pathogens such as Flavobacterium sp., Pseudomonas fluorescens, Vibrio harveyi, Proteus sp. and Vibrio parahaemolyticus. From the present study it can be concluded that Alcaligens faecalis AU01 has the potential for aquaculture as probiotic agent and other several applications.

Antimicrobial and hemolytic activity of seaweed extracts Ulva fasciata (Delile 1813) from Mandapam, Southeast coast of India

Objective To evaluate the In vitro antimicrobial and hemolytic activity of marine macroalgae Ulva fasciata (U. fasciata) collected from Mandapam coastal waters, and to identify certain seaweed extracts that can act as an alternative of commonly used antibiotics. Methods Seaweeds U. fasciata was collected from Gulf of Mannar, Southeast Coastal Region, Mandapam, Tamil Nadu and was screened for antimicrobial and hemolytic activity. Methanol, butanol and aqueous extracts were tested against selected fish pathogens, Aeromonas hydrophila, Pseudomonas fluorescens, Proteus sp. Vibrio alginolyticus (V. alginolyticus) and Enterobacter sp. and fungal pathogens Rhizopus sp., Aspergillus flavus, Aspergillus sp., Aspergillus niger and Candida sp. The extract was subjected to TLC to determine the presences of peptides and amide groups. And the hemolytic activity was assayed. Results Maximum of 16 mm inhibition zone was observed against V. alginolyticus and the minimum 12 mm against Enterobacter sp., respectively. U. fasciata showed poor activity against the fungal pathogens. The present results showed the use of seaweeds as an antimicrobial agents for pharmacology or as a health-promoting food for aquaculture. Conclusions The screening result confirms that these seaweeds can be further studied and used as possible source of antimicrobial compounds.