Abstract
Based on a total of 6,295,650 sequences from the V3 and V4 regions (16S ribosomal RNA), the composition of the microorganism communities in the water of three Litopenaeus vannamei (Decapoda, Whiteleg shrimp; Soc Trang, Vietnam) ponds were identified. Pseudomonas (10–20.29%), Methylophilus (13.26–24.28%), and Flavobacterium (2.6–19.29%) were the most abundant genera. The total ammonia (TAN) concentration (p = 0.025) and temperature (p = 0.015) were significantly correlated with the relative abundance of Pseudomonas in two bacterial communities (ST1, ST4), whereas the predictive functions of microorganism communities based on 16S rRNA gene data was estimated using Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUST), which showed that nitrogen metabolism was significantly negatively correlated (p = 0.049) with TAN concentration. The abundance of Pseudomonas and nitrogen metabolism increased with a decrease in TAN concentration. The correlation between TAN concentration and the abundance of Pseudomonas was followed by the isolation, and heterotrophic nitrifying performance analysis was used to confirm our findings. Six Pseudomonas strains capable of heterotrophic nitrification were isolated from the three water samples and showed a complete reduction of 100 mg/L NH4Cl during a 96-h cultivation. These results indicate the potential of applying Pseudomonas in shrimp ponds for water treatment.
Highlights
Brackish-water aquaculture is a major worldwide source of food production and an economic driver [1]
The analysis of 16S rRNA gene sequences in the V3 to V4 regions from our samples (Table 1) showed that we obtained a total of 6,295,650 high-quality sequences, 99.99% of which were matched as bacteria, while 0.006% were matched as archaea
The highest bacterial richness values, represented by the number of observed Operational Taxonomic unit (OTU) in samples, were observed in Soc Trang–Penaeus monodon (ST-PM) sample and lowest were observed in the ST3 sample
Summary
Brackish-water aquaculture is a major worldwide source of food production and an economic driver [1]. Crustacean aquaculture comprises 57% of the world brackish water culture, in which marine decapod shrimps, primarily comprising Penaeus monodon and Litopenaeus vannamei, accounted for more than 99% of total production in 2010 [2]. Ammonia accumulates rapidly due to natural excretion and high metabolic excretion rate in intensive shrimp ponds during the cultivation life-cycle [3,4]. The concentration of total ammonia nitrogen (TAN) at high levels is toxic to shrimp aquaculture, resulting in post-larvae reduced growth under NH3 concentrations of 0.301 mg/L [4]. Information is lacking regarding environmental effects on the relative abundance of bacteria for the monitoring of water quality in shrimp ponds
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