ABSTRACT
Over the past 15 years, pioneering interdisciplinary research has been performed on the microbiology of hydrogeologically well-defined alpine karst springs located in the Northern Calcareous Alps (NCA) of Austria. This article gives an overview on these activities and links them to other relevant research. Results from the NCA springs and comparable sites revealed that spring water harbors abundant natural microbial communities even in aquifers with high water residence times and the absence of immediate surface influence. Apparently, hydrogeology has a strong impact on the concentration and size of the observed microbes, and total cell counts (TCC) were suggested as a useful means for spring type classification. Measurement of microbial activities at the NCA springs revealed extremely low microbial growth rates in the base flow component of the studied spring waters and indicated the importance of biofilm-associated microbial activities in sediments and on rock surfaces. Based on genetic analysis, the autochthonous microbial endokarst community (AMEC) versus transient microbial endokarst community (TMEC) concept was proposed for the NCA springs, and further details within this overview article are given to prompt its future evaluation. In this regard, it is well known that during high-discharge situations, surface-associated microbes and nutrients such as from soil habitats or human settlements-potentially containing fecal-associated pathogens as the most critical water-quality hazard-may be rapidly flushed into vulnerable karst aquifers. In this context, a framework for the comprehensive analysis of microbial pollution has been proposed for the NCA springs to support the sustainable management of drinking water safety in accordance with recent World Health Organization guidelines. Near-real-time online water quality monitoring, microbial source tracking (MST) and MST-guided quantitative microbial-risk assessment (QMRA) are examples of the proposed analytical tools. In this context, this overview article also provides a short introduction to recently emerging methodologies in microbiological diagnostics to support reading for the practitioner. Finally, the article highlights future research and development needs. This article is categorized under: 1Engineering Water > Water, Health, and Sanitation2Science of Water > Water Extremes3Water and Life > Nature of Freshwater Ecosystems.
ABSTRACT
Seasonal dynamics of naturally occurring prokaryotes, viruses, and heterotrophic nanoflagellates in two hydro-geologically contrasting alpine karst springs were monitored over three annual cycles. To our knowledge, this study is the first to shed light on the occurrence and possible interrelationships between these three groups in karstic groundwater. Hydrological and microbiological standard indicators were recovered simultaneously in order to estimate surface influence, especially during rainfall events. Data revealed a strong dependence of the microbial communities on the prevailing hydrological situation. Prokaryotic numbers averaged 5.1 × 10(7) and 1.3 × 10(7) cells L(-1) , and heterotrophic nanoflagellate abundance averaged 1.1 × 10(4) and 3 × 10(3) cells L(-1) in the limestone spring type (LKAS2) and the dolomitic spring type (DKAS1), respectively. Viral abundance in LKAS2 and DKAS1 averaged 9.4 × 10(8) and 1.1 × 10(8) viruses L(-1) . Unlike in DKAS1, the dynamic spring type LKAS2 revealed a clear difference between base flow and high discharge conditions. The virus-to-prokaryotes ratio was generally lower by a factor of 2-3, at higher average water residence times. Furthermore, the high prokaryotes-to-heterotrophic nanoflagellate ratios, namely about 4700 and 5400 for LKAS2 and DKAS1, respectively, pointed toward an uncoupling of these two groups in the planktonic fraction of alpine karstic aquifers.
Subject(s)
Bacterial Load , Biota , Groundwater/microbiology , Groundwater/virology , Parasite Load , Viral Load , Groundwater/parasitology , SeasonsABSTRACT
Metaproteomics and its potential applications are very promising to study microbial activity in environmental samples and to obtain a deeper understanding of microbial interactions. However, due to the complexity of soil samples the exhaustive extraction of proteins is a major challenge. We compared soil protein extraction protocols in terms of their protein extraction efficiency for two different soil types. Four different protein extraction procedures were applied based on (a) SDS extraction without phenol, (b) NaOH and subsequent phenol extraction, (c) SDS-phenol extraction and (d) SDS-phenol extraction with prior washing steps. To assess the suitability of these methods for the functional analysis of the soil metaproteome, they were applied to a potting soil high in organic matter and a forest soil. Proteins were analyzed by two-dimensional liquid chromatography/tandem mass spectrometry (2D-LC-MS/MS) and the number of unique spectra as well as the number of assigned proteins for each of the respective protocols was compared. In both soil types, extraction with SDS-phenol (c) resulted in "high" numbers of proteins. Moreover, a spiking experiment was conducted to evaluate protein recovery. To this end sterilized forest soil was amended with proteins from pure cultures of Pectobacterium carotovorum and Aspergillus nidulans. The protein recovery in the spiking experiment was almost 50%. Our study demonstrates that a critical evaluation of the extraction protocol is crucial for the quality of the metaproteomics data, especially in highly complex samples like natural soils.
ABSTRACT
Spring waters from alpine karst aquifers are important drinking water resources. To investigate in situ heterotrophic prokaryotic production and its controlling factors, two different alpine karst springs were studied over two annual cycles. Heterotrophic production in spring water, as determined by [(3)H]leucine incorporation, was extremely low ranging from 0.06 to 6.83 pmol C L(-1) h(-1) (DKAS1, dolomitic-karst-spring) and from 0.50 to 75.6 pmol C L(-1) h(-1) (LKAS2, limestone-karst-spring). Microautoradiography combined with catalyzed reporter deposition-FISH showed that only about 7% of the picoplankton community took up [(3)H]leucine, resulting in generation times of 3-684 days. Principal component analysis, applying hydrological, chemical and biological parameters demonstrated that planktonic heterotrophic production in LKAS2 was governed by the respective hydrological conditions, whereas variations in DKAS1 changed seemingly independent from discharge. Measurements in sediments recovered from LKAS2, DKAS1 and similar alpine karst aquifers (n=12) revealed a 10(6)-fold higher heterotrophic production (average 19 micromol C dm(-3) h(-1)) with significantly lower generation times as compared with the planktonic fraction, highlighting the potential of surface-associated communities to add to self-purification processes. Estimates of the microbially mediated CO(2) in this compartment indicated a possible contribution to karstification.
