16 S rRNA gene diversity and gut microbial composition of the Indian white shrimp (Penaeus indicus)

Spätzle maintains homeostasis of hemolymph microbiota in Scylla paramamosain through Toll2

The Toll pathway is crucial for innate immune responses in organisms (including Drosophila and mammals). The Spätzle protein outside of cells acts as a ligand for Toll receptors, enabling the transfer of signals from outside the cell to the inside. However, the function of Spätzle in the immune system of mud crab (Scylla paramamosain) remains unclear. This research discovered a novel Spätzle gene (Sp-Spz) in mud crab, which showed extensive expression in all the tissues that were examined. The RNA interference exhibited the correlation between Sp-Spz and the anti-lipopolysaccharide factors (ALFs). Knockdown of Sp-Spz decreased the expression of Sp-Toll2 but not Sp-Toll1. In Drosophila Schneider 2 cells, Sp-Spz was found interacted with Sp-Toll2. Moreover, the depletion of Sp-Spz caused the separation of hepatic lobules from the basement membrane, resulting in the disruption of the structural coherence of hepatopancreatic cells. Additionally, the knockdown of Sp-Spz resulted in changes to the composition of the hemolymph microbiota, specifically affecting the proportions of different phylum and family levels. The findings indicated that Sp-Spz may promote the synthesis of ALFs via Sp-Toll2, thereby influencing the homeostasis of microbiota in the hemolymph. In this study, novel insights into mud crab immunity are provided.

Exploration of the candidate beneficial bacteria for Penaeus vannamei culture by core microbiome analysis using amplicon sequencing

Globally, Penaeus vannamei is the vital species in aquaculture production. Beneficial bacterial exploration of gut, sediment, and water were investigated in P. vannamei culture using Illumina Miseq sequencing of 16S RNA V3-V4 hypervariable regions. Predominant phyla identified were Proteobacteria, Tenericutes, Bacteroidetes in gut; Proteobacteria, Bacteroidetes, Planctomycetes in sediment and Cyanobacteria, Proteobacteria, and Planctomycetes in water. In total, 46 phyla, 509 families and 902 genera; 70 phyla, 735 families and 1255 genera; 55 phyla, 580 families and 996 genera were observed in gut, sediment and water, respectively. Diversity of microbial communities in respect of observed Operational Taxonomic Units, diversity indices (Shannon and Simpson), richness index (Chao1) were significantly high P (<0.05) in 60 DoC in gut and 30 DoC in sediment. Beta diversity indicated separate clusters for bacterial communities in gut, sediment and water samples and formation of distinct community profiles. Core microbiome in P. vannamei rearing ponds over a time consisted of 9, 21, and 20 OTUs in gut, rearing water and sediment, respectively. This study helps to intervene with suitable beneficial microbes to establish an aquaculture system thereby contributes to enhance the productivity, improve water quality and pond bottom condition, and control the pathogenic agents at each stage of the culture.

Microbial community composition associated with early developmental stages of the Indian white shrimp, Penaeus indicus

Gut microbiota is known to influence the physiology, health, nutrient absorption, reproduction, and other metabolic activities of aquatic organisms. Microbial composition can influence intestinal immunity and are considered as health indicators. Information on gut microbial composition provides potential application possibilities to improve shrimp health and production. In the absence of such information for Penaeus indicus, the present study reports the microbial community structure associated with its early developmental stages. Bacterial community associated with the early developmental stages (egg, nauplii, zoea, mysis, PL1, PL6 and PL12) from two hatchery cycles were analysed employing 16S rRNA high throughput sequencing. Proteobacteria and Bacteroidetes, were the two dominant phyla in P. indicus development stages. Sequential sampling revealed the constant change in the bacterial composition at genus level. Alteromonas was dominant in egg and nauplii stage, whilst Ascidiaceihabitans (formerly Roseobacter) was the dominant genera in both PL6 and PL12. The bacterial composition was highly dynamic in early stages and our study suggests that the mysis stage is the critical phase in transforming the microbial composition and it gets stabilised by early post larval stages. This is the first report on the composition of microbiota in early developmental stages of P. indicus. Based on these results the formation of microbial composition seems to be influenced by feeding at early stages. The study provides valuable information to device intervention strategies for healthy seed production.