Specifically, the green abalone Haliotis fulgens is one of the species that stands out in Mexico due to its commercial exploitation. This is an endemic species of the Baja California Peninsula of fishing importance and with great aquaculture potential. There is evidence that the formulation and preparation of diets with acidic pH favors their stability, allowing greater use and a decrease in production costs. This study investigated the intestinal microbiomes of juvenile green abalone H. fulgens (2.17 ± 0.04 g; 2.61 ± 0.08 cm) with a formulated diet ABKELP® isoprotein (15.52%) and isolipidic (1.51%) with three pH levels (5, 7, 8) and a control with Macrocystis pyrifera for 5.5 months. The intestinal samples (Bacteria 16S V3 + V4 gene, Endophytic Bacteria V5 + V7, Archaeal 16S V4 + V5 and Fungal ITS ITS1–5F, Illumina NovaSeq 6000 Systems gene) were sequenced and the intestinal microbiomes were analyzed.
High molecular weight genomic DNA was extracted, a total of 3 digestive gland samples for each of the diets with the phenol-chloroform extraction procedure (Miller et al., 1988). Genomic DNA was partially sequenced by Illumina protocol to the company in Novogene, USA. The taxonomic profiles of the digestive glands for each dietary condition were determined using the bioinformatics tool QIIME2 (v.2021.8)
At the control treatment, a large amount of OTUs were observed and the majority corresponded to Rhodobacterales, this is one of the most diverse aquatic bacterial group (> 100 genera), producers of the Polyhydroxybutyrate (PHB) polymer, apparently in response to physiological stress conditions, mainly in which nutrients are limited, which works as an energy source causing the highest growth observed in the largest individuals in some marine species that are hosts, such as sea cucumber (Yamazak et al., 2016).
In the treatments with ABKELP® formulated feed of different pH levels, only OTUs of the genus Psychrilyobacter were presented; in other abalone metagenomes works, they mention that Psychrilyobacter have enzymes involved in the acetate pathway and are associated with pyruvate fermentation (Gobet et al., 2018). This fermentation process results in the production of short chain fatty acids (SCFA) that abalone is able to assimilate.
The ABKELP® pH 5 diet, despite having less taxonomic diversity, had greater water stability, as well as a greater predicted functional capacity of the intestinal microbial communities compared to the other treatments, which indicates that this may be a very suitable diet for the successful cultivation of green abalone.