A metagenomic assessment of microbial communities in anaerobic bioreactors and sediments: Taxonomic and functional relationships.

The present study used metagenomic sequencing, metagenome assembly and physical-chemical analysis to describe taxonomically and functionally 3 anaerobic bioreactors treating manure (LI), brewery (BR) and cornmeal (CO) wastes, and an anaerobic estuarine sediment (ES). Proteobacteria, Firmicutes, Euryarchaeota and Bacteroidetes were the most abundant Phyla in all metagenomes. A bacteria/archaea ratio of 3.4 was found in the industrial full-scale anaerobic bioreactors BR and CO, while ratios greater than 10 were found for LI and ES. Canonical correspondence analysis showed that environmental variables such as chemical oxygen demand, lipid content, and ammonium nitrogen influenced the ordination of taxonomic groups. Mesotoga prima was linked to high-temperature conditions, particularly in the BR bioreactor, along with the presence of heat shock proteins genes. Likewise, the hydrogenotrophic methanogen, Methanoregula formicica, was associated with high ammonium concentration in LI bioreactor. The interactions of microbes with specific methanogenic pathways were identified using Clusters of Orthologous Groups (COG) functions, while metagenome-assembled genomes (MAGs) further confirmed relationships between taxa and functions. Our results provide valuable information to understand microbial processes in anaerobic environments.

Welfare Indicators in Tilapia: An Epidemiological Approach.

Interest and concern about rearing methods and their impact on animal welfare have increased. Production evaluation is population-based, and animal welfare analysis should be similar. In fish, the most common welfare indicators are gill state, fin damage, and body condition. The objective of this study was to evaluate the feeding rate effect on the welfare indicators of Oreochromis niloticus using an epidemiological approach. Five growth stages (from 1.2 to 360 g) were studied using four feeding rates as treatments: underfeeding (80%), recommended feeding (100%), and two levels of overfeeding (120% and 140%). The evaluated welfare indicators include the presence of lesions in different body areas and fins, the decrease in body condition index, and their impact on biomass production. Incidence and relative risk were determined for each indicator. Statistically significant associations were found in the indicators of mortality, weight, body condition (K), and presence of evident damage in the caudal and anal fin in all stages. The results showed that the feed rate directly affects the welfare indicators and production. Mortality, weight reduction, K reduction, and caudal and anal fin damage incidence showed to be relevant indicators in all O. niloticus growing stages. As a result of this study, the epidemiological approach seems to be a valuable tool for production. A risk traffic light method is a proposal that could have great potential, with the suggested limits for WI's concerning the individuals present in the culture pond, allowing progressive evaluation and decision-making to correct risky situations.