Advanced wastewater treatment with microalgae-indigenous bacterial interactions

Microalgal-indigenous bacterial wastewater treatment(MBWT)emerges as a promising approach for the concurrent removal of nitrogen(N)and phosphorus(P).Despite its potential,the prevalent use of MBWT in batch systems limits its broader application.Furthermore,the success of MBWT critically depends on the stable self-adaptation and synergistic interactions between microalgae and indigenous bacteria,yet the underlying biological mechanisms are not fully understood.Here we explore the viability and microbial dynamics of a continuous flow microalgae-indigenous bacteria advanced wastewater treatment system(CFMBAWTS)in processing actual secondary effluent,with a focus on varying hydraulic retention times(HRTs).The research highlights a stable,mutually beneficial relationship between indigenous bacteria and microalgae.Microalgae and indigenous bacteria can create an optimal environment for each other by providing essential cofactors(like iron,vitamins,and indole-3-acetic acid),oxygen,dissolved organic matter,and tryptophan.This collaboration leads to effective microbial growth,enhanced N and P removal,and energy generation.The study also uncovers crucial metabolic pathways,functional genes,and patterns of microbial succession.Significantly,the effluent NH4 t-N and P levels complied with the Chinese national Class-II,Class-V,Class-IA,and Class-IB wastewater discharge standards when the HRT was reduced from 15 to 6 h.Optimal results,including the highest rates of CO_(2) fixation(1.23 g L^(-1)),total energy yield(32.35 kJ L^(-1)),and the maximal lipid(33.91%)and carbohydrate(41.91%)content,were observed at an HRT of 15 h.Overall,this study not only confirms the feasibility of CFMBAWTS but also lays a crucial foundation for enhancing our understanding of this technology and propelling its practical application in wastewater treatment plants.

Plant property regulates soil bacterial community structure under altered precipitation regimes in a semi-arid desert grassland, China

Variations of precipitation have great impacts on soil carbon cycle and decomposition of soil organic matter.Soil bacteria are crucial participants in regulating these ecological processes and vulnerable to altered precipitation.Studying the impacts of altered precipitation on soil bacterial community structure can provide a novel insight into the potential impacts of altered precipitation on soil carbon cycle and carbon storage of grassland.Therefore,soil bacterial community structure under a precipitation manipulation experiment was researched in a semi-arid desert grassland in Chinese Loess Plateau.Five precipitation levels,i.e.,control,reduced and increased precipitation by 40%and 20%,respectively(referred here as CK,DP40,DP20,IP40,and IP20)were set.The results showed that soil bacterial alpha diversity and rare bacteria significantly changed with altered precipitation,but the dominant bacteria and soil bacterial beta diversity did not change,which may be ascribed to the ecological strategy of soil bacteria.The linear discriminate analysis(LDA)effect size(LEfSe)method found that major response patterns of soil bacteria to altered precipitation were resource-limited and drought-tolerant populations.In addition,increasing precipitation greatly promoted inter-species competition,while decreasing precipitation highly facilitated inter-species cooperation.These changes in species interaction can promote different distribution ratios of bacterial populations under different precipitation conditions.In structural equation model(SEM)analysis,with changes in precipitation,plant growth characteristics were found to be drivers of soil bacterial community composition,while soil properties were not.In conclusion,our results indicated that in desert grassland ecosystem,the sensitive of soil rare bacteria to altered precipitation was stronger than that of dominant taxa,which may be related to the ecological strategy of bacteria,species interaction,and precipitation-induced variations of plant growth characteristics.

Inter-phylum negative interactions affect soil bacterial community dynamics and functions during soybean development under long-term nitrogen fertilization

Understanding interspecies interactions is essential to predict the response of microbial communities to exogenous perturbation.Herein,rhizospheric and bulk soils were collected from five developmental stages of soybean,which grew in soils receiving 16-year nitrogen inputs.Bacterial communities and functional profiles were examined using high-throughput sequencing and quantitative PCR,respectively.The objective of this study was to identify the key bacterial interactions that influenced community dynamics and functions.We found that the stages of soybean development outcompeted nitrogen fertilization management in shaping bacterial community structure,while fertilization treatments significantly shaped the abundance distribution of nitrogen functional genes.Temporal variations in bacterial abundances increased in bulk soils,especially at the stage of soybean branching,which helps to infer underlying negative interspecies interactions.Members of Cyanobacteria and Actinobacteria actively engaged in inter-phylum negative interactions in bulk soils and soybean rhizosphere,respectively.Furthermore,the negative interactions between nitrogen-fixing functional groups and the reduction of nifH gene abundance were coupled during soybean development,which may help to explain the linkages between population dynamics and functions.Overall,these findings highlight the importance of inter-phylum negative interactions in shaping the correlation patterns of bacterial communities and in determining soil functional potential.