Scholarly Work - Microbiology & Cell Biology
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/3494
Browse
4 results
Search Results
Item Competitive resource allocation to metabolic pathways contributes to overflow metabolisms and emergent properties in cross-feeding microbial consortia(2018-04) Carlson, Ross P.; Beck, Ashley E.; Phalak, Poonam; Fields, Matthew W.; Gedeon, Tomas; Hanley, Luke; Harcombe, W. R.; Henson, Michael A.; Heys, Jeffrey J.Resource scarcity is a common stress in nature and has a major impact on microbial physiology. This review highlights microbial acclimations to resource scarcity, focusing on resource investment strategies for chemoheterotrophs from the molecular level to the pathway level. Competitive resource allocation strategies often lead to a phenotype known as overflow metabolism; the resulting overflow byproducts can stabilize cooperative interactions in microbial communities and can lead to cross-feeding consortia. These consortia can exhibit emergent properties such as enhanced resource usage and biomass productivity. The literature distilled here draws parallels between in silico and laboratory studies and ties them together with ecological theories to better understand microbial stress responses and mutualistic consortia functioning.Item A Lipid-Accumulating Alga Maintains Growth in Outdoor, Alkaliphilic Raceway Pond with Mixed Microbial Communities(2016-01) Bell, Tisza A. S.; Prithiviraj, Bharath; Wahlen, Brad D.; Fields, Matthew W.; Peyton, Brent M.Algal biofuels and valuable co-products are being produced in both open and closed cultivation systems. Growing algae in open pond systems may be a more economical alternative, but this approach allows environmental microorganisms to colonize the pond and potentially infect or outcompete the algal “crop.” In this study, we monitored the microbial community of an outdoor, open raceway pond inoculated with a high lipid-producing alkaliphilic alga, Chlorella vulgaris BA050. The strain C. vulgaris BA050 was previously isolated from Soap Lake, Washington, a system characterized by a high pH (∼9.8). An outdoor raceway pond (200 L) was inoculated with C. vulgaris and monitored for 10 days and then the culture was transferred to a 2,000 L raceway pond and cultivated for an additional 6 days. Community DNA samples were collected over the 16-day period in conjunction with water chemistry analyses and cell counts. Universal primers for the SSU rRNA gene sequences for Eukarya, Bacteria, and Archaea were used for barcoded pyrosequence determination. The environmental parameters that most closely correlated with C. vulgaris abundance were pH and phosphate. Community analyses indicated that the pond system remained dominated by the Chlorella population (93% of eukaryotic sequences), but was also colonized by other microorganisms. Bacterial sequence diversity increased over time while archaeal sequence diversity declined over the same time period. Using SparCC co-occurrence network analysis, a positive correlation was observed between C. vulgaris and Pseudomonas sp. throughout the experiment, which may suggest a symbiotic relationship between the two organisms. The putative relationship coupled with high pH may have contributed to the success of C. vulgaris. The characterization of the microbial community dynamics of an alkaliphilic open pond system provides significant insight into open pond systems that could be used to control photoautotrophic biomass productivity in an open, non-sterile environment.Item Potential Role of Acetyl-CoA Synthetase (acs) & Malate Dehydrogenase (mae) in the Evolution of the Acetate Switch in Bacteria and Archaea(2015-08) Barnhart, Elliott P.; McClure, Marcella A.; Johnson, Kiki; Cleveland, Sean; Hunt, Kristopher A.; Fields, Matthew W.Although many Archaea have AMP-Acs (acetyl-coenzyme A synthetase) and ADP-Acs, the extant methanogenic genus Methanosarcina is the only identified Archaeal genus that can utilize acetate via acetate kinase (Ack) and phosphotransacetylase (Pta). Despite the importance of ack as the potential urkinase in the ASKHA phosphotransferase superfamily, an origin hypothesis does not exist for the acetate kinase in Bacteria, Archaea, or Eukarya. Here we demonstrate that Archaeal AMP-Acs and ADP-Acs contain paralogous ATPase motifs previously identified in Ack, which demonstrate a novel relation between these proteins in Archaea. The identification of ATPase motif conservation and resulting structural features in AMP- and ADP-acetyl-CoA synthetase proteins in this study expand the ASKHA superfamily to include acetyl-CoA synthetase. Additional phylogenetic analysis showed that Pta and MaeB sequences had a common ancestor, and that the Pta lineage within the halophilc archaea was an ancestral lineage. These results suggested that divergence of a duplicated maeB within an ancient halophilic, archaeal lineage formed a putative pta ancestor. These results provide a potential scenario for the establishment of the Ack/Pta pathway and provide novel insight into the evolution of acetate metabolism for all three domains of life.Item Biofilm growth mode promotes maximum carrying capacity and community stability during product inhibition syntrophy(2014-12) Brileya, Kristen A.; Camilleri, Laura B.; Zane, Grant M.; Wall, Judy D.; Fields, Matthew W.Sulfate-reducing bacteria (SRB) can interact syntrophically with other community members in the absence of sulfate, and interactions with hydrogen-consuming methanogens are beneficial when these archaea consume potentially inhibitory H2 produced by the SRB. A dual continuous culture approach was used to characterize population structure within a syntrophic biofilm formed by the SRB Desulfovibrio vulgaris Hildenborough and the methanogenic archaeum Methanococcus maripaludis. Under the tested conditions, monocultures of D. vulgaris formed thin, stable biofilms, but monoculture M. maripaludis did not. Microscopy of intact syntrophic biofilm confirmed that D. vulgaris formed a scaffold for the biofilm, while intermediate and steady-state images revealed that M. maripaludis joined the biofilm later, likely in response to H2 produced by the SRB. Close interactions in structured biofilm allowed efficient transfer of H2 to M. maripaludis, and H2 was only detected in cocultures with a mutant SRB that was deficient in biofilm formation (ΔpilA). M. maripaludis produced more carbohydrate (uronic acid, hexose, and pentose) as a monoculture compared to total coculture biofilm, and this suggested an altered carbon flux during syntrophy. The syntrophic biofilm was structured into ridges (∼300 × 50 μm) and models predicted lactate limitation at ∼50 μm biofilm depth. The biofilm had structure that likely facilitated mass transfer of H2 and lactate, yet maximized biomass with a more even population composition (number of each organism) when compared to the bulk-phase community. Total biomass protein was equivalent in lactate-limited and lactate-excess conditions when a biofilm was present, but in the absence of biofilm, total biomass protein was significantly reduced. The results suggest that multispecies biofilms create an environment conducive to resource sharing, resulting in increased biomass retention, or carrying capacity, for cooperative populations.