1] Department of Microbiology and Molecular Genetics, 6180 Biomedical Physical Sciences, Michigan State University, East Lansing, Michigan 48824, USA.  Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan 48109, USA.
Competition for molecular oxygen (O(2)) among respiratory microorganisms is intense because O(2) is a potent electron acceptor. This competition leads to the formation of microoxic environments wherever microorganisms congregate in aquatic, terrestrial and host-associated communities. Bacteria can harvest O(2) present at low, even nanomolar, concentrations using high-affinity terminal oxidases. Here, we report the results of surveys searching for high-affinity terminal oxidase genes in sequenced bacterial genomes and shotgun metagenomes. The results indicate that bacteria with the potential to respire under microoxic conditions are phylogenetically diverse and intriguingly widespread in nature. We explore the implications of these findings by highlighting the importance of microaerobic metabolism in host-associated bacteria related to health and disease.
"The gut microbiota of healthy individuals is dominated by anaerobic bacteria, which outnumber aerobic and facultative anaerobic bacteria by a factor of 100–1,000:1 (Quigley and Quera, 2006), while the root microbiota is enriched for Proteobacteria, a phylum dominated by aerobic species. Consistent with this, genes encoding high-affinity oxidases that use O 2 as a terminal electron acceptor are overrepresented in gut metagenomes, whereas those encoding low-affinity oxidases are enriched in soil metagenomes (Morris and Schmidt, 2013). "
"In the environment, microbial communities are known to stratify based on oxygen and other chemical gradients (Fenchel and Finlay, 2008; Morris and Schmidt, 2013). CF mucus also contains oxygen gradients (Worlitzsch et al., 2002; Morris and Schmidt, 2013), suggesting that microbes may stratify similarly. Thus the micro-environment of a mucus-filled bronchiole can be considered analogous to the Winogradsky column, developed by Sergei Winogradsky to study the stratification of microbial communities in sediment based on chemical and oxygen gradients (Winogradsky, 1897). "
[Show abstract][Hide abstract] ABSTRACT: There is a poor understanding of how the physiology of polymicrobial communities in cystic fibrosis (CF) lungs contributes to pulmonary exacerbations and lung function decline. In this study, a microbial culture system based on the principles of the Winogradsky column (WinCF system) was developed to study the physiology of CF microbes. The system used glass capillary tubes filled with artificial sputum medium to mimic a clogged airway bronchiole. Chemical indicators were added to observe microbial physiology within the tubes. Characterization of sputum samples from seven patients showed variation in pH, respiration, biofilm formation and gas production, indicating that the physiology of CF microbial communities varied among patients. Incubation of homogenized tissues from an explant CF lung mirrored responses of a Pseudomonas aeruginosa pure culture, supporting evidence that end-stage lungs are dominated by this pathogen. Longitudinal sputum samples taken through two exacerbation events in a single patient showed that a two-unit drop in pH and a 30% increase in gas production occurred in the tubes prior to exacerbation, which was reversed with antibiotic treatment. Microbial community profiles obtained through amplification and sequencing of the 16S rRNA gene showed that fermentative anaerobes became more abundant during exacerbation and were then reduced during treatment where P. aeruginosa became the dominant bacterium. Results from the WinCF experiments support the model where two functionally different CF microbial communities exist, the persistent Climax Community and the acute Attack Community. Fermentative anaerobes are hypothesized to be the core members of the Attack Community and production of acidic and gaseous products from fermentation may drive developing exacerbations. Treatment targeting the Attack Community may better resolve exacerbations and resulting lung damage.
The ISME Journal 12/2014; 9(4). DOI:10.1038/ismej.2014.234 · 9.30 Impact Factor
"The CR of the analyzed water masses did in some cases exhibit pronounced changes with changes in O 2 concentration (Table 2 and Fig. 4), but seen as an average of the measured values for all locations there is very little O 2 dependence above O 2 concentrations of about 500 nmol L À 1 , and the K m values can thus in general be assumed to be below 250 nmol L À 1 . Apparent K m values for these mixed communities below 300–250 nmol L À 1 are not surprising, as even the low affinity terminal oxidases have been reported to have K m values in that range (Morris and Schmidt, 2013). Further Kalvelage and colleagues (Kalvelage et al., 2013) detected genes for high affinity terminal oxidases in the ETSP OMZ waters. "
[Show abstract][Hide abstract] ABSTRACT: Highly sensitive STOX O2 sensors were used for determination of in situ O2 distribution in the eastern tropical north and south Pacific oxygen minimum zones (ETN/SP OMZs), as well as for laboratory determination of O2 uptake rates of water masses at various depths within these OMZs. Oxygen was generally below the detection limit (few nmol L−1) in the core of both OMZs, suggesting the presence of vast volumes of functionally anoxic waters in the eastern Pacific Ocean. Oxygen was often not detectable in the deep secondary chlorophyll maximum found at some locations, but other secondary maxima contained up to ~0.4 µmol L−1. Directly measured respiration rates were high in surface and subsurface oxic layers of the coastal waters, reaching values up to 85 nmol L−1 O2 h−1. Substantially lower values were found at the depths of the upper oxycline, where values varied from 2–33 nmol L−1 O2 h−1. Where secondary chlorophyll maxima were found the rates were higher than in the oxic water just above. Incubation times longer than 20 h, in the all-glass containers, resulted in highly increased respiration rates. Addition of amino acids to the water from the upper oxycline did not lead to a significant initial rise in respiration rate within the first 20 h, indicating that the measurement of respiration rates in oligotrophic ocean water may not be severely affected by low levels of organic contamination during sampling. Our measurements indicate that aerobic metabolism proceeds efficiently at extremely low oxygen concentrations with apparent half-saturation concentrations (Km values) ranging from about 10 to about 200 nmol L−1.
Deep Sea Research Part I Oceanographic Research Papers 12/2014; 94. DOI:10.1016/j.dsr.2014.10.001 · 2.57 Impact Factor
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.