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Biofilm formation inhibition and dispersal of multi-species communities containing ammonia-oxidising bacteria.

ABSTRACT: Despite considerable research, the biofilm-forming capabilities of Nitrosomonas europaea are poorly understood for both mono and mixed-species communities. This study combined biofilm assays and molecular techniques to demonstrate that N. europaea makes very little biofilm on its own, and relies on the activity of associated heterotrophic bacteria to establish a biofilm. However, N. europaea has a vital role in the proliferation of mixed-species communities under carbon-limited conditions, such as in drinking water distribution systems, through the provision of organic carbon via ammonia oxidation. Results show that the addition of nitrification inhibitors to mixed-species nitrifying cultures under carbon-limited conditions disrupted biofilm formation and caused the dispersal of pre-formed biofilms. This dispersal effect was not observed when an organic carbon source, glucose, was included in the medium. Interestingly, inhibition of nitrification activity of these mixed-species biofilms in the presence of added glucose resulted in increased total biofilm formation compared to controls without the addition of nitrification inhibitors, or with only glucose added. This suggests that active AOB partially suppress or limit the overall growth of the heterotrophic bacteria. The experimental model developed here provides evidence that ammonia-oxidising bacteria (AOB) are involved in both the formation and maintenance of multi-species biofilm communities. The results demonstrate that the activity of the AOB not only support the growth and biofilm formation of heterotrophic bacteria by providing organic carbon, but also restrict and limit total biomass in mixed community systems.

SUBMITTER: Keshvardoust P

PROVIDER: S-EPMC6711990 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Biofilm formation inhibition and dispersal of multi-species communities containing ammonia-oxidising bacteria.

Keshvardoust Pejhman P Huron Vanessa A A VAA Clemson Matthew M Constancias Florentin F Barraud Nicolas N Rice Scott A SA

NPJ biofilms and microbiomes 20190827 1

Despite considerable research, the biofilm-forming capabilities of Nitrosomonas europaea are poorly understood for both mono and mixed-species communities. This study combined biofilm assays and molecular techniques to demonstrate that N. europaea makes very little biofilm on its own, and relies on the activity of associated heterotrophic bacteria to establish a biofilm. However, N. europaea has a vital role in the proliferation of mixed-species communities und ...[more]

PMID: 31482007

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Project description:BackgroundSyntrophic acetate oxidation (SAO) is the predominant pathway for methane production in high ammonia anaerobic digestion processes. The bacteria (SAOB) occupying this niche and the metabolic pathway are poorly understood. Phylogenetic diversity and strict cultivation requirements hinder comprehensive research and discovery of novel SAOB. Most SAOB characterised to date are affiliated to the physiological group of acetogens. Formyltetrahydrofolate synthetase is a key enzyme of both acetogenic and SAO metabolism. The encoding fhs gene has therefore been identified as a suitable functional marker, using a newly designed primer pair. In this comparative study, we used a combination of terminal restriction fragment length polymorphism profiling, clone-based comparison, qPCR and Illumina amplicon sequencing to assess the bacterial community and acetogenic sub-community prevailing in high- and low-ammonia laboratory-scale digesters in order to delineate potential SAOB communities. Potential candidates identified were further tracked in a number of low-ammonia and high-ammonia laboratory-scale and large-scale digesters in order to reveal a potential function in SAO.ResultsAll methodical approaches revealed significant changes in the bacterial community composition concurrently with increasing ammonia and predominance of SAO. The acetogenic community under high ammonia conditions was revealed to be generally heterogeneous, but formed distinct phylogenetic clusters. The clusters differed clearly from those found under low-ammonia conditions and represented an acetogenic assemblage unique for biogas processes and recurring in a number of high-ammonia processes, indicating potential involvement in SAO.ConclusionsThe phylogenetic affiliation and population dynamics observed point to a key community, belonging mainly to the Clostridia class, in particular to the orders Clostridiales and Thermoanaerobacterales, which appear to specialise in SAO rather than being metabolically versatile. Overall, the results reported here provide evidence of functional importance of the bacterial families identified in high-ammonia systems and extend existing knowledge of bacterial and acetogenic assemblages at low and high ammonia levels. This information will be of help in monitoring and assessing the impacts on the SAOB community in order to identify characteristics of robust and productive high ammonia biogas processes.

Project description:Polystyrene petri dishes containing liquid medium were inoculated with single-cell suspensions of a fresh clinical isolate of Neisseria subflava and were incubated under conditions of low vibration. N. subflava colonies grew firmly attached to the surface of the dish, while the broth remained clear. Growing colonies released cells into the medium, resulting in the appearance of 10(2) to 10(4) small satellite colonies attached to the surface of the dish in an area adjacent to each mature colony after 24 h. Satellite colonies grew in patterns of streamers shaped like jets and flares emanating from mature colonies and pointing toward the center of the dish. This dispersal pattern evidently resulted from the surface translocation of detached biofilm cells by buoyancy-driven convection currents that were generated due to slight temperature gradients in the medium. Streamers of satellite colonies ranged from 2 to >40 mm in length. Satellite colonies in very long streamers were relatively uniform in size regardless of their distance from the mature colony, suggesting that mature colonies released single cells or small clusters of cells into the medium and that the detachment, surface translocation, and subsequent surface reattachment of released cells were a transitory process. Incubation of N. subflava single cells in a perfused biofilm fermentor resulted in a large spike of the number of CFU in the perfusate after 9.5 h of growth, consistent with a rapid release of cells into the medium. Biofilm colonies of several other phylogenetically diverse oral bacteria, including Actinobacillus actinomycetemcomitans, Haemophilus aphrophilus, Streptococcus mitis, and a prevalent but previously uncultured oral Streptococcus sp., exhibited similar temperature-dependent dispersal patterns in broth culture. This in vitro spreading phenotype could be a useful tool for studying biofilm dispersal in these and other nonflagellated bacteria and may have physiological relevance to biofilm dispersal in the oral cavity.

Project description:Ammonia inhibition is an important reason for reactor failures and economic losses in anaerobic digestion. Its impact on acetic acid degradation is well-studied, while its effect on propionic and butyric acid degradation has received little attention and is consequently not considered in the Anaerobic Digestion Model No. 1 (ADM1). To compare ammonia inhibition of the degradation of these three volatile fatty acids (VFAs), we fed a mixture of them as sole carbon source to three continuous stirred tank reactors (CSTRs) and increased ammonium bicarbonate concentrations in the influent from 52 to 277 mM. The use of this synthetic substrate allowed for the determination of degradation efficiencies for the individual acids. While butyric acid degradation was hardly affected by the increase of ammonia concentration, propionic acid degradation turned out to be even more inhibited than acetic acid degradation with degradation efficiencies dropping to 31 and 65% for propionic and acetic acid, respectively. The inhibited reactors acclimatized and approximated pre-disturbance degradation efficiencies toward the end of the experiment, which was accompanied by strong microbial community shifts, as observed by amplicon sequencing of 16S rRNA genes and terminal restriction fragment length polymorphism (T-RFLP) of mcrA genes. The acetoclastic methanogen Methanosaeta was completely replaced by Methanosarcina. The propionic acid degrading genus Syntrophobacter was replaced by yet unknown propionic acid degraders. The butyric acid degrading genus Syntrophomonas and hydrogenotrophic Methanomicrobiaceae were hardly affected. We hypothesized that the ammonia sensitivity of the initially dominating taxa Methanosaeta and Syntrophobacter led to a stronger inhibition of the acetic and propionic acid degradation compared to butyric acid degradation and hydrogenotrophic methanogenesis, which were facilitated by the ammonia tolerant taxa Syntrophomonas and Methanomicrobiaceae. We implemented this hypothesis into a multi-taxa extension of ADM1, which was able to simulate the dynamics of both microbial community composition and VFA concentration in the experiment. It is thus plausible that the effect of ammonia on VFA degradation strongly depends on the ammonia sensitivity of the dominating taxa, for syntrophic propionate degraders as much as for acetoclastic methanogens.

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Biofilm formation inhibition and dispersal of multi-species communities containing ammonia-oxidising bacteria.

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Biofilm formation inhibition and dispersal of multi-species communities containing ammonia-oxidising bacteria.

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