Microbial Community Response to Carbon-Nitrogen Ratio Manipulation in Biofloc Culture

Abstract

Biofloc technology (BFT) is an alternative aquaculture practice that involves the manipulation of carbon-nitrogen ratio (C:N) to manage nitrogenous waste through microbial assimilation. This study aimed to determine the composition of the microbial community present in BFT and describe the microbial community’s response to C:N manipulation. The experiment had a complete randomized design with two set-ups (i.e., BFT and control) in triplicates. The experimental unit was a 120-L rectangular tank stocked with 15 mixed-sex tilapia fish, Oreochromis niloticus, with an average weight of 15±3 g. The C:N was adjusted to 16:1 using molasses. Illumina MiSeq sequencing platform was used, and bioinformatics was conducted in R using dada2 and phyloseq package. Seventeen (17) phyla were identified, but only seven were remarkably abundant, namely: Proteobacteria, Bacteroidetes, Firmicutes, Actinobacteria, Verrucomicrobia, Planctomycetes, and Fusobacteria. Double Principal Coordinates Analysis (DPCoA), Principal Coordinate Analysis (PCoA) of Weighted Unifrac Distance and Canonical Correspondence Analysis (CCoA) revealed an association of Proteobacteria to low ammonia concentration in BFT treatment. On the other hand, phylum Bacteroidetes was clustered towards the control, characterized by high ammonia. Overall, BFT has increased Shannon and Simpson diversity indices compared to the control. Regime change in the microbial community was not easily caused by organic C supplementation because of community robustness to withstand biotic and abiotic disturbances. Controlled laboratory experiment showed that some bacteria species proliferate as a response to C:N manipulation, but established species remained dominant.

The microbial communities (bacteria, algae, zooplankton, and fungi) improved biofloc technology including the nitrogen-related material cycle in Litopenaeus vannamei farms

“…The algal group mostly consisted of Bacillariophyta (diatom) and Chlorophyta (green algae) containing suspended microalgae ( Car et al, 2020 ; Mohseni et al, 2020 ; Tahir et al, 2020 ). The bacterial group was mainly composed of Bacteroidetes , Chloroflexi , Cyanobacteria , and Proteobacteria ( Kawaichi et al, 2013 ; Chen et al, 2019 ; Liu et al, 2019 ; Zammit, 2019 ; Tanay et al, 2020 ). Species associated with nitrogen-related metabolism may be present among these phyla ( Kawaichi et al, 2013 ; Chen et al, 2019 ; Liu et al, 2019 ; Tanay et al, 2020 ).…”

“…The bacterial group was mainly composed of Bacteroidetes , Chloroflexi , Cyanobacteria , and Proteobacteria ( Kawaichi et al, 2013 ; Chen et al, 2019 ; Liu et al, 2019 ; Zammit, 2019 ; Tanay et al, 2020 ). Species associated with nitrogen-related metabolism may be present among these phyla ( Kawaichi et al, 2013 ; Chen et al, 2019 ; Liu et al, 2019 ; Tanay et al, 2020 ). Additionally, Cyanobacteria is involved in nitrogen-related metabolism through functions such as photosynthesis and nitrogen fixation ( Zammit, 2019 ).…”

“…The bacterial group in the studied microbial communities contained 12 major species. These bacterial species have been detected and reported in sources involved in the elimination of substances such as ammonia and nitrates ( Kawaichi et al, 2013 ; Chen et al, 2019 ; Liu et al, 2019 ; Zammit, 2019 ; Tanay et al, 2020 ), e.g., sewage treatment plants, and have been studied for their involvement in nitrogen-related metabolic processes such as nitrification and denitrification ( Liu et al, 2019 ; Abakari et al, 2020 ; D’Silva and Kyndt, 2020 ). Additionally, the Cyanobacteria L. cavernicola can photosynthesize and is expected to function similarly to members of the algal group ( Zammit, 2019 ).…”

“…Additionally, the Cyanobacteria L. cavernicola can photosynthesize and is expected to function similarly to members of the algal group ( Zammit, 2019 ). Furthermore, several previous studies have shown that the synthesis of proteins by bacteria is involved in the ammonia and nitrogen cycles and in nitrate-related metabolism ( Liu et al, 2019 ; Tanay et al, 2020 ). Given these diverse metabolic functions, members of the bacterial group would not be limited to ecological roles as decomposers but may also serve as producers ( Riley and Gordon, 1999 ; Denef and Banfield, 2012 ).…”

“…Given these diverse metabolic functions, members of the bacterial group would not be limited to ecological roles as decomposers but may also serve as producers ( Riley and Gordon, 1999 ; Denef and Banfield, 2012 ). Given that prokaryotic microbial communities in the studied shrimp farms had higher species richness and diversity than the eukaryotic microbial communities, the major species of the bacterial group were diverse, and their nitrogen-related metabolism and ecological roles are likely to be multifarious ( Liu et al, 2019 ; Abakari et al, 2020 ; Tanay et al, 2020 ).…”