The potential for bioaugmentation of sand filter materials from waterworks using bacterial cultures degrading 4-chloro-2-methylphenoxyacetic acid

Successional trophic complexity and biogeographical structure of eukaryotic communities in waterworks' rapid sand filters

As groundwater-fed waterworks clean their raw inlet water with sand filters, a variety of pro- and eukaryotic microbial communities develop on these filters. While several studies have targeted the prokaryotic sand filter communities, little is known about the eukaryotic communities, despite the obvious need for knowledge of microorganisms that get in contact with human drinking water. With a new general eukaryotic primer set (18S, V1-V3 region), we performed FLX-454 sequencing of material from 21 waterworks' sand filters varying in age (3-40 years) and geographical location on a 250 km east-west axis in Denmark, and put the data in context of their previously published prokaryotic communities. We find that filters vary highly in trophic complexity depending on age, from simple systems with bacteria and protozoa (3-6 years) to complex, mature systems with nematodes, rotifers and turbellarians as apex predators (40 years). Unlike the bacterial communities, the eukaryotic communities display a clear distance-decay relationship that predominates over environmental variations, indicating that the underlying aquifers feeding the filters harbor distinct eukaryotic communities with limited dispersal in between. Our findings have implications for waterworks' filter management, and offer a window down to the largely unexplored eukaryotic microbiology of groundwater aquifers.

Autochthonous Bioaugmentation-Modified Bacterial Diversity of Phenanthrene Degraders in PAH-Contaminated Wastewater as Revealed by DNA-Stable Isotope Probing

To reveal the mechanisms of autochthonous bioaugmentation (ABA) in wastewater contaminated with polycyclic aromatic hydrocarbons (PAHs), DNA-stable-isotope-probing (SIP) was used in the present study with the addition of an autochthonous microorganism Acinetobacter tandoii LJ-5. We found LJ-5 inoculum produced a significant increase in phenanthrene (PHE) mineralization, but LJ-5 surprisingly did not participate in indigenous PHE degradation from the SIP results. The improvement of PHE biodegradation was not explained by the engagement of LJ-5 but attributed to the remarkably altered diversity of PHE degraders. Of the major PHE degraders present in ambient wastewater ( Rhodoplanes sp., Mycobacterium sp., Xanthomonadaceae sp. and Enterobacteriaceae sp.), only Mycobacterium sp. and Enterobacteriaceae sp. remained functional in the presence of strain LJ-5, but five new taxa Bacillus, Paenibacillus, Ammoniphilus, Sporosarcina, and Hyphomicrobium were favored. Rhodoplanes, Ammoniphilus, Sporosarcina, and Hyphomicrobium were directly linked to, for the first time, indigenous PHE biodegradation. Sequences of functional PAH-RHD_α genes from heavy fractions further proved the change in PHE degraders by identifying distinct PAH-ring hydroxylating dioxygenases between ambient degradation and ABA. Our findings indicate a new mechanism of ABA, provide new insights into the diversity of PHE-degrading communities, and suggest ABA as a promising in situ bioremediation strategy for PAH-contaminated wastewater.

Conservative tracer bromide inhibits pesticide mineralisation in soil

Bromide is a conservative tracer that is often applied with non-conservative solutes such as pesticides to estimate their retardation in the soil. It has been applied in concentrations of up to 250 g Br L-1, levels at which the growth of single-celled organisms can be inhibited. Bromide applications may therefore affect the biodegradation of non-conservative solutes in soil. The present study investigated the effect of potassium bromide (KBr) on the mineralisation of three pesticides - glyphosate, MCPA and metribuzin - in four agricultural A-horizon soils. KBr was added to soil microcosms at concentrations of 0, 0.5, 2.5 and 5 g Br- L-1 in the soil solution. The study concluded that KBr had a negative effect on pesticide mineralisation. The inhibitory effect varied depending on the KBr concentration, the type of pesticide and the type of soil. Furthermore, 16 S amplicon sequencing revealed that the KBr treatment generally reduced the abundance of bacteroidetes and proteobacteria on both an RNA and DNA level. Therefore, in order to reduce the effect of KBr on the soil bacterial community and consequently also on xenobiotic degradation, it is recommended that KBr be applied in a concentration that does not exceed 0.5 g Br- L-1 in the soil water.

Bioaugmentation potential of free and formulated 2,6-dichlorobenzamide (BAM) degrading Aminobacter sp. MSH1 in soil, sand and water

Pesticides are used extensively worldwide, which has led to the unwanted contamination of soil and water resources. Former use of the herbicide 2,6-dichlorobenzonitrile (dichlobenil) has caused pollution of ground and surface water resources by the stable degradation product 2,6-dichlorobenzamide (BAM) in several parts of Europe, which has resulted in the costly closure of several drinking water wells. One strategy for preventing this in future is bioaugmentation using bacterial degraders. BAM-degrading Aminobacter sp. MSH1 was therefore formulated into dried beads and tests undertaken to establish their potential for use in the remediation of polluted soil, sand and water. The formulation procedure included freeze drying, combined with trehalose addition for cell wall protection, thus ensuring a high amount of viable cells following prolonged storage at room temperature. The beads were round-shaped pellets with a diameter of about 1.25 mm, a dry matter content of approximately 95 % and an average viable cell content of 4.4 × 10(9) cells/g bead. Formulated MSH1 cells led to a similar, and frequently even faster, BAM mineralisation (20-65 % (14)CO2 produced from (14)C-labelled BAM) in batch tests conducted with sand, water and different soil moisture contents compared to adding free cells. Furthermore, the beads were easy to handle and had a shelf life of several months.

Draft Genome Sequence of MCPA-Degrading Sphingomonas sp. Strain ERG5, Isolated from a Groundwater Aquifer in Denmark

Sphingomonas sp. strain ERG5 was isolated from a bacterial community, originating from a groundwater aquifer polluted with low pesticide concentrations. This bacterium degrades 2-methyl-4-chlorophenoxyacetic acid (MCPA) in a wide spectrum of concentrations and has been shown to function in bioaugmented sand filters. Genes associated with MCPA degradation are situated on a putative conjugative plasmid.