Antibacterial activity of a marine bacterium against pathogenic and environmental isolates of vibrio species

The marine environment covers three quarters of the surface of the planet is estimated to be home to more than 80% of life and yet it remains largely unexplored. The rich diversity of marine flora and fauna and its adaptation to the harsh marine environment coupled with new developments in biotechnology, has opened up a new exciting vista for extraction of bioactive products of use in medicine. In this study inhibitory activity of a marine bacterium isolated from gut of ribbonfish was studied against pathogenic and environmental isolates of Vibrio species. This strain was identified as Pseudomonas stutzeri and it was found active against V. harveyi (luminescent bacteria), V. cholerae, V. alginolyticus, V. damseal, V. fluvialis. The antibacterial substance produced by Pseudomonas stutzeri was soluble in organic solvent and closely bound to external surface of bacterial cells. Reduction of the absorbance of the V. cholera cell suspension was observed when log phase cells of V. cholerae were treated with MIC and 4xMIC concentration of crude extract of Pseudomonas stutzeri.

Assessment Method for Leaf Litters Allelopathic Effect on Cyanobacteria

A new bioassay technique combining leaf disk and softagar over-layer methods was developed to investigate the allelopathic effect of deciduous leaf litters on the growth of cyanobacteria ( Microcystis aeruginosa Kütz.). Bioactive substances exuded from leaf disks caused inhibitory plaques on the agar plate containing cyanobacteria , and the rate of diffusion depended on the specific leaf disk area. Most of the leaf litters collected around reservoirs in Japan showed inhibitory activity to M. aeruginosa , with Rhus trichocarpa Miq., Quercus variabilis Blume and Mallotus japonicus (Thunb.) Muell. Arg. being the strongest among the 22 tested species.(PDF has 4 pages.)

Antibacterial marine bacterium deter luminous vibriosis in shrimp larvae

Inhibitory activity of a marine pigmented bacterium - Alteromonas sp. - isolated from Penaeus monodon Fabricius larva against pathogenic and environmental isolates of Vibrio harveyi was studied. All the isolates were inhibited to varying degrees by Alteromonas sp. in vitro. The antibacterial substance produced by the Alteromonas sp. was soluble in organic solvent and closely bound to the external surface of bacterial cells. The antibacterial Alteromonas sp., when allowed to colonize on shrimp larvae, suppressed the activity of V. harveyi M3 and reduced mortality of P. monodon larvae in vivo.

Inhibition of seafood-borne bacteria in cooked mackerel (Rastrelliger kanagurta) fish meat by lactic acid bacteria

Antagonistic activity of lactic acid bacteria (LAB) namely Streptococcus faecalis, Pediococcus cerevisiae and Lactobacillus casei was tested against seafood-borne bacteria such as Staphylococcus aureus, Bacillus cereus, Escherichia coli, Clostridium perfringens and Listeria monocytogenes. Three lactic acid bacteria such as Streptococcus faecalis, Lactobacillus casei and Pediococcus cerevisiae were coated on cooked mackerel meat, individually and in combination against fish-borne bacteria. S. faecalis inhibited C. perfringens in individual coat by 3.7 log units as compared to control, whereas L. casei did not inhibit C. perfringens. P. cerevisiae inhibited S. aureus by 5 log units. L. casei, inhibited L. monocytogenes by 3.3 log units on the third day of storage as compared to control. On the other hand, S. aureus and B. cereus were inhibited on the third and second day by 4.9 log and 5.2 log units respectively. B. cereus, S. aureus, L. monocytogenes were the most sensitive to all three LAB. C. perfringens was the least inhibited among all the seafood-borne bacteria tried. Multiple LAB or LAB strains in combination showed much earlier inhibitory activity on seafood-borne bacteria than single LAB coat.

Studies on phenolase enzyme in prawns. II. The inhibitory action on the enzyme by certain chemical agents

The effect of certain chemical agents on dopa oxidation by phenolases has been examined. Sulphur containing amino carboxylic acids are inhibitory agents for dopa oxidation. Tyrosine, a substrate for the enzyme also acts as an inhibitor for dopa oxidation by the enzyme. The possible mode of action has been discussed. The function of diethyl dithiocarbamate in suppressing the display of enzyme activity has been detailed and its behaviour has been compared to the other chemical agents studied.