Identification and characterization of microorganisms potentially beneficial for intensive cultivation of Penaeus vannamei under biofloc conditions: Highlighting Exiguobacterium acetylicum

Abstract

The aim of this work was to isolate, identify and characterize microorganisms present in intensive nursery of Penaeus vannamei during the spontaneous generation of the biofloc and to verify among the isolates, beneficial strains for the intensive cultivation of shrimp under biofloc conditions. 91 strains were isolated and identified by molecular taxonomy. Then, the strains were analysed for the presence of the aiiA gene responsible for the inherited transmission for the production of lactonase.Only Exiguobacterium acetylicum presented the expressed aiiA gene. E. acetylicum was tested for its proteolytic, amylolytic and lipolytic inhibition activity. Inhibition capacity against pathogenic bacteria was 1.47 mm, 2.0 mm and 1.5 mm halo for Vibrio alginolyticus V. harveyi and V. parahaemolyticus, respectively. The mass production process of the E. acetylicum inoculum was standardized at a concentration of 1.58 x 107 CFU/ ml and was applied in two treatments with three replicates each. One group received a weekly application of the inoculum while another group received a biweekly application. A control group received no application of the inoculum. Then, the effect of enriching the intensive culture medium for P. vannamei with E. acetylicum under biofloc conditions was evaluated. At the end of the 21-day trial, the survival and average productivity were statistically higher in the groups that received the application of the bacterial inoculum. The data suggest that the presence of E. acetylicum bacteria in the growth phase of P. vannamei significantly increased survival (90.9 ± 6.0%) and productivity (1.42 ± 0.16 kg/m 3 ).

Competitive interactions between culturable bacteria are highly non-additive

“…Scarce are the environments on Earth not colonized by bacteria. In addition to naturally playing important roles from driving biogeochemical cycles at the ecosystem level ( Cavicchioli et al, 2019 ; Arrigo, 2005 ; Falkowski et al, 2008 ) to supporting host health at the individual level ( Berendsen et al, 2012 ; Manor et al, 2020 ; Gilbert et al, 2018 ), bacteria have also been harnessed for countless biotechnological applications across industries such as food preservation ( Motarjemi, 2002 ), plant and animal health ( Berendsen et al, 2012 ; Júnior et al, 2021 ), biocontrol of pathogens ( Köhl et al, 2019 ), as well as decomposition of toxic compounds, and production of valuable ones ( Varjani et al, 2017 ; Ro et al, 2006 ; Fang and Smith, 2016 ; Mainka et al, 2021 ). In natural environments, bacteria often form rich and complex communities, but understanding how these communities organize has proven difficult ( Widder et al, 2016 ).…”

In silico prediction of potential indigenous microbial biomarkers in Penaeus vannamei identified through meta-analysis and genome-scale metabolic modelling

“…Furthermore, the leading genera revealed in this study's healthy state, namely Acinetobacter and Candidatus Bacilloplasma, were reported to act as a central hub connecting the significant bacterial population in the network of healthy shrimp hepatopancreas [ 51 ]. Further, Exiguobacterium genera in the healthy state have improved growth and survival in P. vannamei and provided probiotic advantages [ 7 , 11 ]. Lactobacillus members identified in this study are known probiotics and have been extensively studied for their abilities to maintain animal health [ 50 ].…”

Microorganisms as a sustainable aquafeed ingredient: A review

“…For example, due to their ability to utilize many organic substrates, microorganisms have been used to maintain water quality, particularly by the autotroph nitrifying bacteria. In addition, their role in controlling pathogens in disease management and minimizing environmental impacts in the system has also been widely documented (de Mello Júnior et al, 2021; Martínez‐Córdova et al, 2017; Ortiz‐Estrada et al, 2020).…”