Shrimps are the tiny free-swimming crustacean, typically marine and possess commercial importance as food. In Thailand and other countries; aqua farming of marine shrimps is accelerated because of its high economic worth1. But unfortunately, shrimps are being highly affected by elevated proportion nitrogenous compounds which produce from the excretion of aquatic animals, exceed feeding (aquaculture) and discharge from terrestrial environments. Nitrogen compounds particularly ammonia and nitrite are highly lethal for aquatic life and leads towards eutrophication in aquatic ecosystems2,3.
Partial changing of fresh water in shrimp ponds is temporary and costly method to get rid of this situation. Moreover, this technique leads towards transfer of shrimp pathogens to environments causing more intensive water pollution2. Consequently, this issue should be addressed by treating nitrogenous water without water exchanging.
Affected water can also be treated through nitrification which is performed by nitrifying bacteria. Nitrification is a biological process consists of 2 steps, firstly, ammonia (NH3) is converted to nitrite (NO2‾) and secondly, nitrite is transformed to nitrate (NO3‾) having less toxicity for aquatic life4. Bacteria with the group of Nitrosomonas, Nitrosococcus, Nitrosolobus and the group of Nitrobacter, Nitrococcus, Nitrospira are generally documented as the groups of Ammonium Oxidizing Bacteria AOB and Nitrite Oxidizing Bacteria NOB, respectively4. But, their performance gets affected due to high concentration of ammonia5 and being autotrophic they are also slow-growing.
Therefore, Scientists have discovered another genus of bacteria genus Halomonas which is salt loving and their habitats are generally saline environments6,7. Genus Halomonas is Gram-negative, heterotrophic, fast-growing and salt-tolerant bacteria. Furthermore, it is reported that Halomonas is also involved in nitrification process. Therefore, Yutthapong Sangnoi and team conducted an experiment to isolate native heterotrophic halophilic Halomonas spp. and to evaluate their nitrogen removal effectiveness. In this experiment, Halomonas species, were isolated by culturing of samples obtained from shrimp pond into modified Pep-Beef-AOM medium. Nitrification capability was checked and monitored by nitrite reagent. Scientists also calculated the ammonium removal efficiency by the standard colorimetric technique. Identification and classification of this species were investigated by morphological, physiological and biochemical characters and molecular information as well.
Sangoni and colleagues noted all strains exhibited the attributes of salt-loving and ammonium removal skill under elevated ammonium concentration. Some new species were also identified other than Halomonas spp. Halomonas spp., isolates were assigned the term “nitrifying bacteria” because of their ammonium removal and nitrite producing capabilities. Conclusively, this study can help to develop efficient microbial product for treating saline ammonium waste water.
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17 November, 2019