Summary
Natural attenuation of the mono‐aromates benzene, toluene, ethylbenzene and xylene occurs under iron‐reducing conditions in a leachate‐contaminated aquifer near the Banisveld landfill, the ...Netherlands. The diversity of mono‐aromate‐degrading microorganisms was studied by targeting functional genes encoding benzylsuccinate synthase α‐subunit (bssA) and 6‐oxocyclohex‐1‐ene‐1‐carbonyl‐CoA hydrolase (bamA). Sixty‐four bssA and 188 bamA variants were sequenced from groundwater sampled along the pollution plume in 1999 and 2004. Species containing bssA sequences closest affiliated (> 91%) with the betaprotebacterium Georgfuchsia toluolica were the dominant alkylbenzene degraders (89% of bssA sequences). bssA genes were found at more than 10‐fold lower copy numbers than bamA genes, of which only a small fraction (< 2%) was closely related to the genes of Georgfuchsia. bamA gene diversity was high and bamA‐based community composition was primarily affected by dissolved organic carbon (DOC) and ferrous iron concentrations. bamA sequences closest related to Geobacteraceae were dominantly (43.2%) observed and the presence of Geobacteraceae‐related bamA sequences was associated with DOC. Our results indicate a key role for specialized Georgfuchsia spp. in the degradation of alkylbenzenes, whereas Geobacteraceae are involved in degradation of aromatics other than toluene and xylene.
Oil absorbent particles made from surface-modified polypropylene can be used to facilitate the removal of oil from the environment. In this study, we investigated to what extent absorbed oil was ...biodegraded and how this compared to the biodegradation of oil in water. To do so, we incubated two bacterial communities originating from the Niger Delta, an area subject to frequent oil spills, in the presence and absence of polypropylene particles. One community evolved from untreated soil whereas the second evolved from soil pre-exposed to oil. We observed that the polypropylene particles stimulated the growth of biofilms and enriched species from genera
,
and
. Cultures with polypropylene particles degraded more crude oil than those where the oil was present in suspension regardless of whether they were pre-exposed or not. Moreover, the community pre-exposed to crude oil had a different community structure and degraded more oil than the one from untreated soil. We conclude that the biodegradation rate of crude oil was enhanced by the pre-exposure of the bacterial communities to crude oil and by the use of oil-absorbing polypropylene materials. The data show that bacterial communities in the biofilms growing on the particles have an enhanced degradation capacity for oil.
We determined the degradation rates of the herbicides 2,4-D and 2,4,5-T by two different bacterial communities. One of these originated from soil heavily contaminated with herbicides from Bien Hoa ...airbase, the other from the same soil but amended with additional carbon and Gibbs energy sources. The community from the contaminated, but untreated, soil degraded both 2,4-D and 2,4,5-T within 5 days of cultivation. The one from the amended soil, however, hardly showed any degradation of the compounds throughout 23 days of cultivation. After refreshment of the medium and prolonged culturing, however, this community degraded both herbicides within 25 days with progressively increasing rates. nMDS analysis revealed a highly significant differentiation pattern of the two communities. Cultures inoculated with amended soil showed a significant increase of
Bacillus
and
Paenibacillus
upon prolonged exposure to the herbicides. The succession in the culture from untreated soil, on the other hand, was dominated by species from the Proteobacteria. We were able to isolate two of them and they were shown to be related to
Bordetella petrii
and
Sphingomonas histidinilytica
, successively. Subsequent PCR analyses of their DNA revealed the presence of key genes involved in the degradation of the herbicides. This study provides a more fundamental understanding of the biodegradation of 2,4-D and 2,4,5-T by displaying part of the bacterial community succession during their breakdown allowing a comprehensive view on potential key degraders.
Four bacterial strains were isolated from enrichment cultures inoculated with soil from Bien Hoa military base in Vietnam contaminated with the herbicides 2,4-dichlorophenoxyacetate (2,4-D) and ...2,4,5-trichlorophenoxyacetate (2,4,5-T). They were classified as
Pseudomonas aeruginosa
BT1 2.2,
Sphingomonas histidinilytica
BT1 5.2,
Bordetella petrii
BT1 9.2, and
Achromobacter xylosoxidans
BT1 10.2. All four were able to degrade 2,4-D and 2,4,5-T, but only the last three species used them as the sole sources of carbon and energy. Mass balance analyses suggest that between 33 and 46% of the carbon in the herbicides is incorporated into dry weight (DW). We obtained insight into their degradation pathways by the genomic analysis of these strains. A
tfdCDEF
gene cluster was found in
A. xylosoxidans
BT1 10.2 with amino acid sequences of their gene products showing high identity to those in
B. petrii
DSM12804.
Bordetella petrii
BT1 9.2 has a full complement of the
tfdABCDEF
genes. Surprisingly, the gene organization along with the amino acid sequences of the gene products are virtually identical to those of
Cupriavidus pinatubonensis
JMP134, referred to as type I
tfd
genes, and different from those of
A. xylosoxidans
BT1 10.2 and
B. petrii
DSM12804. We hypothesize that some of the genetic potential to degrade the herbicides has been recruited in recent mating events between these species and other members of the proteobacteria. This is the first report showing that
B. petrii
BT1 9.2 emerges as a key player in the degradation of 2,4-D.
Summary
The potential for dissimilatory ferric iron Fe(III) reduction in intertidal sediments of the polluted Scheldt estuary, Northwest Europe, was assessed by combining field‐based geochemical ...measurements with laboratory experiments on the associated microbiology. Microbial communities at a freshwater and brackish location were characterized by culture‐independent 16S rRNA gene analysis, as well as enrichments, strain isolation and physiological screening. Dilution‐to‐extinction batch enrichments using a variety of Fe(III) sources were performed. The dilution factor of the inoculum in the enrichments had a more determining effect on the Fe(III)‐reducing microbial community structure than the Fe(III) source. Well‐known Fe(III) reducers, including members of the family Geobacteraceae and the genus Shewanella, constituted only a small fraction (≤ 1%) of the in situ microbial community. Instead, facultative anaerobic Ralstonia and strictly anaerobic, spore‐forming Clostridium species dominated Fe(III) reduction. These species were able to utilize a variety of electron acceptors. This flexibility may help the organisms to survive in the dynamic estuarine environment. The high diversity and abundance of culturable Fe(III) reducers (4.6 × 105 and 2.4 × 104 cells g−1 sediment at the freshwater and brackish site respectively), plus the high concentrations of chemically reducible solid‐phase Fe(III) at the sites, implied a high potential for dissimilatory Fe(III) reduction in the estuarine sediments. Pore water chemical data further supported in situ dissimilatory Fe(III) reduction.
Chronic exposure of children in sub-Saharan Africa to aflatoxins has been associated with low birth weight, stunted growth, immune suppression, and liver function damage.
species have been shown to ...reduce aflatoxin contamination during the process of food fermentation. Twenty-three
s strains were isolated from fecal samples obtained from a cohort of rural Ugandan children at the age of 54 to 60 months, typed by 16S rRNA gene sequencing, and characterized in terms of their ability to bind aflatoxin B
in vitro. Evidence for chronic exposure of these children to aflatoxin B
in the study area was obtained by analysis of local foods (maize flour and peanuts), followed by the identification of the breakdown product aflatoxin M
in their urine samples. Surprisingly,
in the gut microbiota of 140 children from the same cohort at 24 and 36 months showed the highest positive correlation coefficient with stunting among all bacterial genera identified in the stool samples. This correlation was interpreted to be associated with dietary changes from breastfeeding to plant-based solid foods that pose an additional risk for aflatoxin contamination, on one hand, and lead to increased intake of
species on the other.
A key question in microbial ecology is what the driving forces behind the persistence of large biodiversity in natural environments are. We studied a microbial community with more than 100 different ...types of species which evolved in a 15-years old bioreactor with benzene as the main carbon and energy source and nitrate as the electron acceptor. Using genome-centric metagenomics plus metatranscriptomics, we demonstrate that most of the community members likely feed on metabolic left-overs or on necromass while only a few of them, from families Rhodocyclaceae and Peptococcaceae, are candidates to degrade benzene. We verify with an additional succession experiment using metabolomics and metabarcoding that these few community members are the actual drivers of benzene degradation. As such, we hypothesize that high species richness is maintained and the complexity of a natural community is stabilized in a controlled environment by the interdependencies between the few benzene degraders and the rest of the community members, ultimately resulting in a food web with different trophic levels.
Millions of people worldwide are at risk of arsenic poisoning from their drinking water. In Bangladesh the problem extends to rural drinking water wells, where non-biological solutions are not ...feasible. In serial enrichment cultures of water from various Bangladesh drinking water wells, we found transfer-persistent arsenite oxidation activity under four conditions (aerobic/anaerobic; heterotrophic/autotrophic). This suggests that biological decontamination may help ameliorate the problem. The enriched microbial communities were phylogenetically at least as diverse as the unenriched communities: they contained a bonanza of 16S rRNA gene sequences. These related to
,
,
,
and
species. In addition, the enriched microbiomes contained genes highly similar to the arsenite oxidase (
) gene of chemolithoautotrophic (e.g.,
sp. SY) and heterotrophic arsenite-oxidizing strains. The enriched cultures also contained
phylotypes not detected in the previous survey of uncultivated samples from the same wells. Anaerobic enrichments disclosed a wider diversity of arsenite oxidizing
phylotypes than did aerobic enrichments. The cultivatable chemolithoautotrophic and heterotrophic arsenite oxidizers are of great interest for future
or
arsenic bioremediation technologies for the detoxification of drinking water by oxidizing arsenite to arsenate that should then precipitates with iron oxides. The microbial activities required for such a technology seem present, amplifiable, diverse and hence robust.
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