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Oxygen limitation within a bacterial aggregate.

ABSTRACT: ABSTRACT Cells within biofilms exhibit physiological heterogeneity, in part because of chemical gradients existing within these spatially structured communities. Previous work has examined how chemical gradients develop in large biofilms containing >10(8) cells. However, many bacterial communities in nature are composed of small, densely packed aggregates of cells (? 10(5) bacteria). Using a gelatin-based three-dimensional (3D) printing strategy, we confined the bacterium Pseudomonas aeruginosa within picoliter-sized 3D "microtraps" that are permeable to nutrients, waste products, and other bioactive small molecules. We show that as a single bacterium grows into a maximally dense (10(12) cells ml(-1)) clonal population, a localized depletion of oxygen develops when it reaches a critical aggregate size of ~55 pl. Collectively, these data demonstrate that chemical and phenotypic heterogeneity exists on the micrometer scale within small aggregate populations. IMPORTANCE Before developing into large, complex communities, microbes initially cluster into aggregates, and it is unclear if chemical heterogeneity exists in these ubiquitous micrometer-scale aggregates. We chose to examine oxygen availability within an aggregate since oxygen concentration impacts a number of important bacterial processes, including metabolism, social behaviors, virulence, and antibiotic resistance. By determining that oxygen availability can vary within aggregates containing ? 10(5) bacteria, we establish that physiological heterogeneity exists within P. aeruginosa aggregates, suggesting that such heterogeneity frequently exists in many naturally occurring small populations.

SUBMITTER: Wessel AK

PROVIDER: S-EPMC3994514 | biostudies-literature | 2014 Apr

REPOSITORIES: biostudies-literature

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Oxygen limitation within a bacterial aggregate.

Wessel Aimee K AK Arshad Talha A TA Fitzpatrick Mignon M Connell Jodi L JL Bonnecaze Roger T RT Shear Jason B JB Whiteley Marvin M

mBio 20140415 2

ABSTRACT Cells within biofilms exhibit physiological heterogeneity, in part because of chemical gradients existing within these spatially structured communities. Previous work has examined how chemical gradients develop in large biofilms containing >10(8) cells. However, many bacterial communities in nature are composed of small, densely packed aggregates of cells (≤ 10(5) bacteria). Using a gelatin-based three-dimensional (3D) printing strategy, we confined the bacterium Pseudomonas aeruginosa ...[more]

PMID: 24736225

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Project description:Methane and ammonia have to be removed from wastewater treatment effluent in order to discharge it to receiving water bodies. A potential solution for this is a combination of simultaneous ammonia and methane oxidation by anaerobic ammonia oxidation (anammox) bacteria and nitrite/nitrate-dependent anaerobic methane oxidation (N-damo) microorganisms. When applied, these microorganisms will be exposed to oxygen, but little is known about the effect of a low concentration of oxygen on a culture containing these microorganisms. In this study, a stable coculture containing anammox and N-damo microorganisms in a laboratory scale bioreactor was established under oxygen limitation. Membrane inlet mass spectrometry (MIMS) was used to directly measure the in situ simultaneous activity of N-damo, anammox, and aerobic ammonia-oxidizing microorganisms. In addition, batch tests revealed that the bioreactor also harbored aerobic methanotrophs and anaerobic methanogens. Together with fluorescence in situ hybridization (FISH) analysis and metagenomics, these results indicate that the combination of N-damo and anammox activity under the continuous supply of limiting oxygen concentrations is feasible and can be implemented for the removal of methane and ammonia from anaerobic digester effluents. IMPORTANCE Nitrogen in wastewater leads to eutrophication of the receiving water bodies, and methane is a potent greenhouse gas; it is therefore important that these are removed from wastewater. A potential solution for the simultaneous removal of nitrogenous compounds and methane is the application of a combination of nitrite/nitrate-dependent methane oxidation (N-damo) and anaerobic ammonia oxidation (annamox). In order to do so, it is important to investigate the effect of oxygen on these two anaerobic processes. In this study, we investigate the effect of a continuous oxygen supply on the activity of an anaerobic methane- and ammonia-oxidizing coculture. The findings presented in this study are important for the potential application of these two microbial processes in wastewater treatment.

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Oxygen limitation within a bacterial aggregate.

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Oxygen limitation within a bacterial aggregate.

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