Minor differences in sand physicochemistry lead to major differences in bacterial community structure and function after exposure to synthetic acid mine drainage

Abstract

The formation of environmentally toxic acidic waste from mining activities is a world-wide problem. Neutralization of this waste can be accomplished by physicochemical and/or biological means. In this short-term study, synthetic acid mine drainage was added to sandfilled mesocosms containing silica-dominated (quartz) sand. Glucose was added as a carbon source for microbial iron and/or sulphate reduction. Replicates contained two separate batches of sand obtained from the same quarry site. The investigations used to assess and compare the chemical and biological functioning of the replicates included system hydraulic conductivity measurements, sand chemistry, effluent chemistry and bacterial community fingerprinting. Minor differences in composition of the sand, including the levels of available nutrients and micronutrients, resulted in major differences in measured parameters. 2 Significant differences in effluent chemistry were found in systems containing different batches of sand. It was demonstrated that the characteristics of the sand and the presence of acid mine drainage impacted the bacterial community structure and function. The importance of the physical substrate on the selection of functional microbial communities in systems remediating AMD should not be under-estimated. The physical substrate should be carefully selected and it may be prudent to include small-scale comparative studies in each particular setting prior to full-scale implementation.

Effects of naturally occurring grit on the reactor performance and microbial community structure of membrane bioreactors

“…Nonetheless, the silica particles or grit in the mixed liquor can interact with the microbes by acting as a bacteria carrier or changing the structure of the sludge flocs, eventually changing the bacterial community structure of the mixed liquor. This assumption could be supported by a previous finding that subtle differences in the properties of sand led to considerable differences in the bacterial community [7].…”

“…Although the grit does not contribute to biological reactions directly, these particles can be potentially involved in the formation of sludge flocs; e.g., small grit can be entrapped by sludge flocs. Because of the high specific area, the grit could be considered as a bacterial media that can affect the growth of the bacteria and thus change the structure of the bacterial community [7,8].…”

Water regime history drives responses of soil Namib Desert microbial communities to wetting events

“…However, the effect of water regime history might be balanced by several salts, such as Ca + , K + , Na + as well as S content, which all presented substantial variations between the riverbed and gravel plain soils, although not significantly different (p > 0.05). As an extreme example, it has indeed been shown that even minor differences in sand crystal composition can lead to completely distinct microbial community structures 43 .…”

Namib Desert dune/interdune transects exhibit habitat-specific edaphic bacterial communities

“…Our data do indicate that fine grains, silts and clays [VFS, SC, ST, CY] are positively correlated with metals [Fe/Mn/Al], minerals [Ca/Mg] and some nutrients (C, P, NO − 3 -N, NH + 4 -N) (Figure 2 ). This suggests that the relationship between bacterial diversity, soil structure and nutrient contents needs further investigation in dune soils as subtle differences in sand mineralogy and micronutrient contents has been shown to significantly impact edaphic community structuring (Welz et al, 2014 ).…”