Seasonal distribution of luminous bacteria in the sediments of a tropical estuary.

Abstract

The qualitative and quantitative distribution and seasonal variation of luminous bacteria in the sediments of Vellar estuary, Porto Novo, South India (11° 29'N, 79° 46'E) was studied. The luminous bacterial population ranged from 5.1 x 103 to 3.2 x 104 CFU/g dry weight in station I and 2.4 x 103 to 9.1 x 103 CFU/g dry weight in station II. The salinity of the estuarine water appeared to have an indirect relationship with luminous bacterial counts in the sediment. The maximum number of luminous bacteria were recorded during summer followed by a decline before the monsoon. The counts were at a low level during monsoon and then started to increase after the monsoon season. Vibrio harveyi, V. fischeri and Photobacterium leiognathi were the species recorded in the sediments. V. harveyi was the dominant species being present throughout the year.Luminous bacteria are widely distributed in the marine environment, from surface to deep water and from the equator to the polar regions. They are ecologically versatile, present in water, sediment and also harboured in the light organs of some fish and gut of many marine organisms (7). Though the association of these bacteria with water and marine animals has been well studied, not much information is available on their densities and distribution in sediments. Hence the present study has been undertaken to elucidate the qualitative and quantitative distribution and the seasonal variation of luminous bacteria in tropical estuarine sediments. MATERIALS AND METHODSSediment samples were collected for a period of one year (from April, 1981 to March, 1982 from two stations in the Vellar estuary located at Porto Novo (11 0

The virulence of Enterococcus to freshwater prawn Macrobrachium rosenbergii and its immune resistance under ammonia stress

“…Ramesh et al [32] also suggested that environmental parameters influence the growth of luminous bacteria. Smith [33] indicated that fast-growing pathogens could overwhelm the initial, non-specific defense and cause disease before more powerful immune defences can operate fully.…”

Effect of cultivation broth pH, temperature and NaCl concentration on virulence of an Enterococcus-like bacterium to the giant freshwater prawn Macrobrachium rosenbergii

“…They also reported that exposure of V harveyi to pH 5.5 significantly reduced ~t s pathogenicity. Ramesh et al (1989) reported that environmental parameters influence the growth of luminous bacteria. Weinberg (1985) reported that environmental variables affecting toxin production are considerably narrower than those for growth of producer cells.…”

Inhibition of Luminescence and Virulence in the Black Tiger Prawn ( Penaeus monodon ) Pathogen Vibrio harveyi by Intercellular Signal Antagonists

“…Additionally, a significant reduction in the toxicity of concentrated supernatant extracts from V. harveyi cultures incubated in the presence of the signal antagonist, as measured by in vivo toxicity assays in mice and prawns, was observed. These results suggest that intercellular signaling antagonists have potential utility in the control of V. harveyi prawn infections.Vibrio harveyi is a gram-negative, luminescent, marine bacterium isolated both in a free-living state (16,17,20) and as a commensal organism in the enteric contents of marine animals (11,22). Recognized as a primary pathogen of many commercially cultured invertebrate species, such as the black tiger prawn (Penaeus monodon), V. harveyi can cause up to 100% mortality of larvae in the hatchery stage of penaeid culture (12,16).…”

“…Vibrio harveyi is a gram-negative, luminescent, marine bacterium isolated both in a free-living state (16,17,20) and as a commensal organism in the enteric contents of marine animals (11,22). Recognized as a primary pathogen of many commercially cultured invertebrate species, such as the black tiger prawn (Penaeus monodon), V. harveyi can cause up to 100% mortality of larvae in the hatchery stage of penaeid culture (12,16).…”