Effect of physical and biological factors on the viability of Vibrio harveyi
ผลของปัจจัยทางกายภาพและชีวภาพต่อความอยู่รอดของ Vibrio harveyi
Somrak Panphon, D. of Sci., F. of Sci. and Tech., PSU.
Niyom Kamlangdee, School of Biology, Institute of Science, Walailuk U., Nakhon Si Thammarat
Grant : Government Budget
Published : Research Report
Key words : Vibrio harveyi, viability of Vibrio harveyi, marine pathogenic bacteria
The marine pathogenic bacteria, identified as Vibrio harveyi, was isolated from infected shrimps (Penaeus monodon Fabricius) and luminous seawater collected from shrimp ponds. It was found that V. harveyi showed significant morphology, physiology and some biochemical characteristics including luminescent on Luminous media and a green and round colony on TCBS agar. The bacteria produced enzymes such as catalase, oxidase, amylase, gelatinase and lipase and acids from fermentation of
various sugars including glucose, fructose, mannitol, mannose, moltose, galactose, trehalose and cellobiose. However, it did not produced gas from glucose fermentation. In addition, it could not grow in peptone water containing 0 and 10% of NaCl and at 5oC.
The effects of salinity, temperature, disinfectants and biological factors on the viability of V. harveyi were investigated. It was shown that the numbers of the bacteria cells (CFU/ml) reached
highest peaks at 48th hours at salinity levels of 30, 40 and 20 ppt, respectively and then decreased gradually at slower rates than other salinity levels. The numbers of V. harveyi cells decreased fasted
at 5 and 10 ppt of seawater, respectively after 48th hours and they were not found in 0 ppt of seawater at 12th hours. After incubation at three different temperatures for 48 hours, V. harveyi showed maxi-
mum growth at room temperature and then decreased gradually, the numbers of bacteria cells de-creased fastest at 40oC while showing a slight decrease at 20oC. The effects of disinfectants including chlorine, povidone iodine, and formalin were studied. It was found that V. harveyi (9.4x106 CFU/ml) were completely disinfected by 4 ppm of chlorine within 30 minutes or 2 ppm within 60 minutes. Povidone iodine at the concentrations of 8 ppm and 6 ppm (active ingredient) completely disinfected V. harveyi (9.2x106 CFU/ml) within 30 and 60 minutes, respectively. In this study, V. harveyi (8.5x
106 CFU/ml) were partially decreased by 100 ppm of formalin within 60 minutes. In addition, the co-culture of V. harveyi with B. Subtilis at different concentrations revealed a decrease in the numbers
of bacteria cells (CFU/ml). The amounts of B. subtilis higher than those of V. harveyi were found to effectively decrease the numbers of bacteria cells.
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