16S rRNA sequences of Exiguobacterium spp. bacteria dominant in a biofloc pond cultured with whiteleg shrimp, Penaeus vannamei

Abstract

Biofloc technology is being applied increasingly in shrimp aquaculture. Many countries have adopted this technology to increase shrimp aquaculture production. Owing to its major importance, this study was conducted to identify the bacterial population from biofloc aquaculture shrimp pond water of Singkir Laut, Kedah, Malaysia. Samples of mature biofloc were collected from the biofloc pond water at different shrimp ages (day of culture [DOC]): DOC30, DOC60 and DOC90. Overall, 43 sequences of bacterial species were blasted, which were identified as Exiguobacterium spp., Bacillus spp., Vibrio spp., Acinetobacter junii, Cobetia marina, Rheinheimera aquimaris and Pseudoalteromonas spp. These bacterial species were identified mostly from heterotrophic plate count agar. The bacterial species of Exiguobacterium aestuarii, Exiguobacterium profundum and Exiguobacterium aurantiacum were identified with 16S rRNA gene sequence similarities of 98.45–99.44%. Bacterial species of Bacillus pumilus, Bacillus velezensis, Bacillus cereus, Bacillus safensis and Bacillus subtilis were identified with 16S rRNA gene sequence similarities of 98.81–99.21%. Bacterial species of Vibrio diazotrophicus, Vibrio diabolicus, Vibrio natriegens and Vibrio harveyi were identified with 16S rRNA gene sequence similarities of 98.03–99.19%. Bacteria from Rheinheimera aquimaris were also identified with 16S rRNA gene sequence similarities of 98.69–99.26%; this bacterium is a novel bacterium identified from biofloc samples of the present study and has not been reported from biofloc samples in any previous study. Exiguobacterium spp. from the novel strains of E. aestuarii and E. profundum were identified as dominant, with 23 of 43 samples isolated from a shrimp pond at time points DOC30, DOC60 and DOC90; these bacteria are Gram‐variable rod‐shaped organisms that are capable of producing extracellular enzyme activity to break down chemical structures, thereby helping to remove organic compounds from aquaculture waste. Exiguobacterium spp. are usually identified in tidal flat sediments and on muddy sea coasts. This discovery is consistent with the site of the shrimp pond near to a muddy beach area, which might be the source of seawater leading to the predominance of this type of bacteria in the biofloc samples in the studied pond.

Evaluation of Salipiger thiooxidans and Exiguobacterium aestuarii from the Saemangeum Reservoir as Potential Probiotics for Pacific White Shrimp (Litopenaeus vannamei)

“…In a previous study, it was reported that Salipiger sp. can remove organic compounds, such as nitrite, from wastewater, and E. aestuarii has recently been shown to effectively eliminate such compounds from aquaculture wastewater through extracellular enzymatic activity [36,70]. In this study, it was confirmed that the water quality in the rearing water was improved due to the denitrification action by the two microorganisms.…”

“…and Salipiger sp. were dominant in stock water, and these bacteria provided a favorable environment for shrimp farming by removing organic compounds from aquaculture waste [35,36]. Despite the advantages that can be utilized as probiotics, research on these microorganisms is lacking compared to that on Bacillus and Lactobacillus, which are relatively active in research.…”

Effects of Nano-Aerators on Microbial Communities and Functions in the Water, Sediment, and Shrimp Intestine in Litopenaeus vannamei Aquaculture Ponds

“…Studies have shown that the use of Acinetobacter KU011TH as a probiotic for juvenile catfish significantly improves lysozyme activity and respiratory activity in the body [ 40 ]. Some species of Exiguobacterium are gram-variable, rod-shaped organisms capable of producing extracellular enzymatically active substances to break down chemical structures to remove organic compounds from aquaculture waste [ 41 ]. Ekasari et al [ 42 ] demonstrated that the addition of Chlorella_sp.…”

Biofloc Technology in Improving Shellfish Aquaculture Production – A Review

“…and bacteria from species Rheinheimera aquimaris where identified dominated by Exiguobacterium spp. (Manan et al, 2022). Thus, it can be concluded that biofloc it contains diversity of microbes or bacterial from beneficial group such as Bacillus sp.…”