New Insights into the Relationships between Bacterial Dynamics and Water Quality of Aquaculture Systems Supplemented with Carbon Source and Biofilm Substratum

Aquaculture is crucial for achieving the FAO’s goal of a world without hunger and malnutrition. Recently, biofilm substratum has been proposed as an effective means to control waste pollution caused by excessive nutrient inputs from aquaculture, but key bacterial communities involved in the remediation remain unclear. Here we reported a freshwater mesocosm study where the addition of biofilm substrata with external carbon effectively controlled the total ammonia nitrogen and improved fish growth. 16S rRNA study and Weighted UniFrac analysis revealed that bacterial compositions were significantly different (999 permutations, p-value < 0.01) between the biofilm-substrata-added and biofilm-substrata-free systems. Planctomycetes were found, as key bacteria benefited from the biofilm substrata addition and exerted the major function of ammonia nitrogen control. Our study demonstrated that the addition of biofilm substrata and an external carbon source favored fish growth and improved the aquaculture environment by the formation of a unique bacteria community.

Diurnal oscillations in gut bacterial load and composition eclipse seasonal and lifetime dynamics in wild meerkats

Circadian rhythms in gut microbiota composition are crucial for metabolic function, yet the extent to which they govern microbial dynamics compared to seasonal and lifetime processes remains unknown. Here, we investigate gut bacterial dynamics in wild meerkats (Suricata suricatta) over a 20-year period to compare diurnal, seasonal, and lifetime processes in concert, applying ratios of absolute abundance. We found that diurnal oscillations in bacterial load and composition eclipsed seasonal and lifetime dynamics. Diurnal oscillations were characterised by a peak in Clostridium abundance at dawn, were associated with temperature-constrained foraging schedules, and did not decay with age. Some genera exhibited seasonal fluctuations, whilst others developed with age, although we found little support for microbial senescence in very old meerkats. Strong microbial circadian rhythms in this species may reflect the extreme daily temperature fluctuations typical of arid-zone climates. Our findings demonstrate that accounting for circadian rhythms is essential for future gut microbiome research.

Multiple macroecological laws do characterize various aspects of microbiota dynamics

In this letter we address the potential confusion related to our recent demonstration that multiple macroecological laws describe short- and long-term dynamics of microbial communities. Specifically, we clarify that these laws, similarly to many other relationships observed in nature, are characterized not just by the existence of scaling, but also by certain characteristic values of the scaling exponents. By performing proper statistical analysis, we demonstrate that the relationships sensitive to temporal bacterial dynamics are not reproduced in the shuffled data. We also discuss that there is no clear evidence in the data that macroecological relationships in microbiota are primarily driven by external or environmental factors. Proper statistical analyses of the data suggest that the dynamics of gut microbiota, even on a constant diet, contains rich temporal structure. Therefore, it is likely that complex and non-linear internal dynamics may be primarily responsible for the observed macroecological laws in microbiota and other ecological communities.

Habitats Are More Important Than Seasons in Shaping Soil Bacterial Communities on the Qinghai-Tibetan Plateau

Both habitats and seasons can determine the dynamics of microbial communities, but the relative importance of different habitats and seasonal changes in shaping the soil bacterial community structures on a small spatial scale in permafrost areas remains controversial. In this study, we explored the relative effect of four typical alpine meadow habitats (swamp wetland, swamp meadow, meadow and mature meadow) versus seasons on soil bacterial communities based on samples from the Qinghai-Tibetan Plateau in four months (March, May, July and September). The results showed that habitats, rather than seasons explained more variation of soil bacterial composition and structure. Environmental cofactors explained the greatest proportion of bacterial variation observed and can help elucidate the driving force of seasonal changes and habitats on bacterial communities. Soil temperature played the most important role in shaping bacterial beta diversities, followed by soil total nitrogen and pH. A group of microbial biomarkers, used as indicators of different months, were identified using random forest modeling, and for which relative abundance was shaped by different environmental factors. Furthermore, seasonality in bacterial co-occurrence patterns was observed. The data showed that co-occurrence relationships changed over months. The inter-taxa connections in May and July were more pronounced than that in March and September. Bryobacter, a genus of subgroup_22 affiliated to Acidobacteria, and Pseudonocardia belonging to Actinobacteria were observed as the keystone taxa in different months in the network. These results demonstrate that the bacterial community was clustered according to the seasonal mechanism, whereas the co-occurrence relationships changed over months, which indicated complex bacterial dynamics in a permafrost grassland on the eastern edge of Qinghai-Tibetan.