In aquatic systems, bacterial community succession is a function of top-down and bottom-up factors, but little information exists on “sideways” controls, such as bacterial predation by Bdellovibrio -like organisms (BLOs), which likely impacts nutrient cycling within the microbial loop and eventual export to higher trophic groups. Here we report transient response of estuarine microbiota and BLO spp. to tidal-associated dissolved organic matter supply in a river-dominated estuary, Apalachicola Bay, Florida. Both dissolved organic carbon and dissolved organic nitrogen concentrations oscillated over the course of the tidal cycle with relatively higher concentrations observed at low tide. Concurrent with the shift in dissolved organic matter (DOM) supply at low tide, a synchronous increase in numbers of bacteria and predatorial BLOs were observed. PCR-restriction fragment length polymorphism of small subunit rDNA, cloning, and sequence analyses revealed distinct shifts such that, at low tide, significantly higher phylotype abundances were observed from γ- Proteobacteria , δ- Proteobacteria , Bacteroidetes , and high G+C Gram-positive bacteria. Conversely, diversity of α- Proteobacteria , β- Proteobacteria , and Chlamydiales-Verrucomicrobia group increased at high tides. To identify metabolically active BLO guilds, tidal microcosms were spiked with six ¹³ C-labeled bacteria as potential prey and studied using an adaptation of stable isotope probing. At low tide, representative of higher DOM and increased prey but lower salinity, BLO community also shifted such that mesohaline clusters I and VI were more active; with an increased salinity at high tide, halotolerant clusters III, V, and X were predominant. Eventually, ¹³ C label was identified from higher micropredators, indicating that trophic interactions within the estuarine microbial food web are potentially far more complex than previously thought.

Humans are inextricably linked to each other and our natural world, and microorganisms lie at the nexus of those interactions. Microorganisms form genetically flexible, taxonomically diverse, and biochemically rich communities, i.e., microbiomes that are integral to the health and development of macroorganisms, societies, and ecosystems.

Bacteria associated with the Eastern oysters ( Crassostrea virginica ) native to Apalachicola Bay, FL, were investigated using 16S rRNA gene amplicon metagenomic sequencing which revealed that the oyster microbiome was predominated by Cyanobacteria and Proteobacteria . We also found that the oyster tissues were predominated by the pathogenic and symbiotic Photobacterium spp. (formerly known as Vibrio damsela e).

Freshwater scarcity and regulations on wastewater disposal have necessitated the reuse of treated wastewater (TWW) for soil irrigation, which has several environmental and economic benefits. However, TWW irrigation can cause nutrient loading to the receiving environments. We assessed bacterial community structure and associated biogeochemical changes in soil plots irrigated with nitrate-rich TWW (referred to as pivots) for periods ranging from 13 to 30 years. Soil cores (0 to 40 cm) were collected in summer and winter from five irrigated pivots and three adjacently located nonirrigated plots. Total bacterial and denitrifier gene abundances were estimated by quantitative PCR (qPCR), and community structure was assessed by 454 massively parallel tag sequencing (MPTS) of small-subunit (SSU) rRNA genes along with terminal restriction fragment length polymorphism (T-RFLP) analysis ofnirK,nirS, andnosZfunctional genes responsible for denitrification of the TWW-associated nitrate. Soil physicochemical analyses showed that, regardless of the seasons, pH and moisture contents (MC) were higher in the irrigated (IR) pivots than in the nonirrigated (NIR) plots; organic matter (OM) and microbial biomass carbon (MBC) were higher as a function of season but not of irrigation treatment. MPTS analysis showed that TWW loading resulted in the following: (i) an increase in the relative abundance ofProteobacteria, especiallyBetaproteobacteriaandGammaproteobacteria; (ii) a decrease in the relative abundance ofActinobacteria; (iii) shifts in the communities of acidobacterial groups, along with a shift in thenirKandnirSdenitrifier guilds as shown by T-RFLP analysis. Additionally, bacterial biomass estimated by genus/group-specific real-time qPCR analyses revealed that higher numbers of total bacteria,Acidobacteria,Actinobacteria,Alphaproteobacteria, and thenirSdenitrifier guilds were present in the IR pivots than in the NIR plots. Identification of thenirK-containing microbiota as a proxy for the denitrifier community indicated that bacteria belonged to alphaproteobacteria from theRhizobiaceaefamily within the agroecosystem studied. Multivariate statistical analyses further confirmed some of the above soil physicochemical and bacterial community structure changes as a function of long-term TWW application within this agroecosystem.

Social and political policy, human activities, and environmental change affect the ways in which microbial communities assemble and interact with people. These factors determine how different social groups are exposed to beneficial and/or harmful microorganisms, meaning microbial exposure has an important socioecological justice context.