Physiological Profiling and Functional Diversity of Groundwater Microbial Communities in a Municipal Solid Waste Landfill Area

Abstract

The disposal of municipal solid wastes in landfills represents a major threat for aquifer environments at the global scale. The aim of this study was to explore how groundwater geochemical characteristics can influence the microbial community functioning and the potential degradation patterns of selected organic substrates in response to different levels of landfill-induced alterations. Groundwaters collected from a landfill area were monitored by assessing major physical-chemical parameters and the microbiological contamination levels (total coliforms and fecal indicators-Colilert-18). The aquatic microbial community was further characterized by flow cytometry and Biolog EcoPlates TM assay. Three groundwater conditions (i.e., pristine, mixed, and altered) were identified according to their distinct geochemical profiles. The altered groundwaters showed relatively higher values of organic matter concentration and total cell counts, along with the presence of fecal indicator bacteria, in comparison to samples from pristine and mixed conditions. The kinetic profiles of the Biolog substrate degradation showed that the microbial community thriving in altered conditions was relatively more efficient in metabolizing a larger number of organic substrates, including those with complex molecular structures. We concluded that the assessment of physiological profiling and functional diversity at the microbial community level could represent a supportive tool to understand the potential consequences of the organic contamination of impacted aquifers, thus complementing the current strategies for groundwater management.

The Biolog EcoPlate™ Technique for Assessing the Effect of Metal Oxide Nanoparticles on Freshwater Microbial Communities

“…The highest shift occurred in the use of carboxylic acids; the initial use (15–17%) in the control increased to 30–57% at 20 and 100 mg/L nZnO level. This was in accordance with Teng et al [ 56 ] and Melita et al [ 57 ], who also found that carboxylic acids were sensitive carbon sources. These substrates are products of organic matter degradation in surface waters; therefore, carboxylic acids belong to the labile organic matter sources of the aquatic environment.…”

“…The use rates of different substrate classes (SAWCD) have rarely been applied in Biolog EcoPlate™ studies, although they can provide important and complementary information to the frequently applied endpoints. Substrates which are promptly and preferentially used may indicate important information on the environmental conditions [ 57 ]. Interestingly, the use of carboxylic acids showed an increasing trend over time at concentrations of 20 and 100 mg/L nZnO.…”

Redox conditions and a moderate anthropogenic impairment of groundwater quality reflected on the microbial functional traits in a volcanic aquifer

“…The microbial community resident in the oxidizing redox facies showed a metabolic profile reported for resource limited and low energy environment, characterized by a relatively low prokaryotic biomass, metabolic potential and functional diversity with respect to that in the reducing facies (Griebler and Lueders 2009). In Ox − , the low affinity to most of the Biolog substrates could indicate a relatively low metabolic versatility of the microbial community to adapt to newly available substrates, as previously reported for subsurface aquatic environments in pristine conditions (Griebler and Avramov 2015;Melita et al 2019). This result might imply a relatively high vulnerability of this ecosystem, since the resident microbial communities are likely unable to degrade complex organic compounds they may accidentally enter in contact with (e.g., organic pollutants).…”

“…The communitylevel physiological profile (CLPP) was estimated by the analysis of each single substrate utilized by the microbial community. The functional diversity was assessed through the application of the Shannon-Wiener's diversity index (H) (Melita et al 2019).…”

Assessment of Different Contaminants in Freshwater: Origin, Fate and Ecological Impact

“…Changes in groundwater quality, such those induced by municipal solid waste disposal in landfills, can directly affect the functional properties of aquatic microbial communities. Melita et al [13] explored the structural alterations, as well as the functional responses, of groundwater microbial communities to a gradient of geochemical alterations induced by a municipal solid waste landfill in central Italy. The microbial communities were characterized by flow cytometry and the Biolog EcoPlates TM assay, with the aim of highlighting biogeochemical cycling patterns along the gradient.…”