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Biology of Methanogenesis and Anaerobic Bioremediation

Regulatory pathways in the methanogenic Archaea, archaeal survival mechanisms in extreme environments, methanogenic biomass conversion in land-based aquaculture systems, biological in situ remediation of organochlorines; bioprocess scale-up of microorganisms from extreme environments.


Kevin R. Sowers, Ph.D. is an anaerobic microbiologist with over 30 years experience in biomass conversion to methane and bioremediation.  Dr. Sowers received his doctoral degree in anaerobic microbiology from Virginia Tech studying conversion of giant brown kelp to biomethane with support from the Gas Research Institute and conducted postdoctoral research at UCLA on the molecular biology of methanogenesis with support from the Office of Navel Research.  He joined the University of Maryland Biotechnology Institute in 1991 and he is currently a professor and associate chair in the Department of Marine Biotechnology, University of Maryland Baltimore County, and associate director of the Institute of Marine & Environmental Technology.  Current research projects include the application of methanogenic processes for waste management in land-based recirculating mariculture systems and development of novel approaches for in situ bioremediation of PCBs in sediments. Additional experience includes the identification and isolation of difficult-to-grow microorganisms with unique degradation capabilities and scale-up of biomass for in-situ applications.  He has presented his research at over 100 scientific meetings and over 60 national and international invited lectures.  His research has generated over 75 peer-reviewed journal articles, 20 book chapters, and several patents and has been featured in radio interviews, newspaper articles and museum exhibits.  He is a member of AAAS, ACS, ASM and SIM, has been an editorial board member for the Journal of Bacteriology, Frontiers in Microbiology and Archaea, and served as a reviewer for numerous domestic and international granting agencies and peer-reviewed journals. 


Research interests

Biology of the Methanogenic Archaea  

The Archaea, Bacteria and Eucarya represent the three primary phylogenetic lineages that diverged and evolved from a common progenote. The controlled expression of gene products involved in methanogenesis is essential for complete biomass conversion and bioremediation in anaerobic sediments, however, the mechanisms of catabolic gene regulation in the third lineage, the Archaea, is not yet known. This research program is divided into three projects.  1) Mechanisms of gene transcription focuses on understanding the mechanisms of gene expression in catabolic pathways of methangenesis.  2) Defining the limits of life focuses understanding the physiological and molecular mechanisms that enable these microorganisms to survive periods of stress including exposure to oxygen and desiccation on earth and as a model for survival on other planets.  3) Biomass conversion in a zero-discharge recirculating mariculture system focuses on efficiency, stability and applicability of a methanogenic consortium as an end process for the digestion of highly saline marine and brackish water aquaculture sludge.  For more details, go to the Sowers' Lab Homepage.

Biological In situ Remediation of Polychlorinated Biphenyls (PCBs)   

Aquatic sediments are the ultimate global sinks for accumulation of chlorinated hydrocarbons such as polychlorinated biphenyls (PCBs) where reductive dehalogenation (halorespiration) has a significant role in their biotransformation. Understanding this microbial process is critical for making management decisions concerning both remediation and risk assessment of PCB-impacted water bodies.  This program focuses on reducing the concentration of polychlorinated biphenyls (PCBs) in sediments by in-situ remediation with PCB degrading microorganisms.  The approach, which employes introduction of anaerobic halorespiring and aerobic PCB oxidizing microorganisms as biofilms on granulated activated carbon, achieves three major objectives: 1) convenient deployment and inoculation of biocatalysts into sediment, 2) immediate reduction of PCB bioavailability to the aquatic food chain through sequestration on the carbon surface, and 3) reduction of in situ PCB concentrations in impacted sediments by dechlorination and subsequent oxidative degradation of the PCBs.  In mesocosm studies PCBs in both freshwater and saline sediments are effectively reduced by 80% within 180 days after treatment.  Field demonstrations are currently underway.  For more details, go to the Sowers' Lab Homepage.


Recent publications

Quinn, B., E.E. Apolinario, A. Gross and K.R. Sowers.  2016.  Characterization of a microbial consortium that converts mariculture fish waste to biomethane.  Aquaculture 453: 154-162.


Aruety, T., T. Brunner, Z. Ronen, A. Gross, K. Sowers and D. Zilberg.  2015.  The fate of the fish pathogen Streptococcus iniae in a sludge digester of a zero discharge recirculating aquaculture system (RAS).  Aquaculture 450: 335-341

Hale, D. B.V. Kjellerup, K.R. Sowers and I. Imamoglu2015.  Evaluation of PCB dechlorination pathways in anaerobic sediment microcosms using an anaerobic dechlorination model.  Journal of Hazardous Materials 296: 120-127.  [ABSTRACT]

Sowers, K.R.  2015.  Methanogenesis. In: Caplan, M.J. (ed.), Reference Module in Biomedical Sciences. Elsevier, Inc., doi:10.1016/B978-0-12-801238-3.90004-7.

Lombard, N.J., U. Ghosh, B.V. Kjellerup, K.R. Sowers.  2014.  Kinetics and threshold level of 2,3,4,5-tetrachlorobiphenyl dechlorination by an organohalide respiring bacterium.  Env. Sci. Technol. 48(8): 4353-4360.  [ABSTRACT]

Kjellerup, B.V., C. Naff, S.J. Edwards, U. Ghosh, J.E. Baker, K.R. Sowers.  2014.  Effects of activated carbon on reductive dechlorination of PCBs by halorespiring bacteria indigenous in sediment.  Wat. Res. 52: 1-10 [ABSTRACT]

Jasso-Chávez, R., E.E. Apolinario, K.R. Sowers, and J.G. Ferry.  2013. MrpA Functions in Energy Conversion During Acetate-Dependent Growth of Methanosarcina acetivorans. J. Bacteriol. 195(17): 3987-94  [ABSTRACT]

Payne, R.B., S.K. Fagervold, H.D. May and K.R. Sowers. 2013. Remediation of polychlorinated biphenyl impacted sediment by concurrent bioaugmentation with anaerobic dehalorespiring and aerobic degrading bacteria.  Env. Sci & Tech. 47(8): 3807-3815.  [ABSTRACT] 

Sowers, K.R. and H.D. May. 2013. In situ treatment of PCBs by anaerobic microbial dechlorination in aquatic sediment: are we there yet?  Curr. Opin. Biotechnol. 24: 482-488.   [ABSTRACT]

Chun, C.L., R.B. Payne, K.R. Sowers, and H.D. May. 2012. Electrical stimulation of microbial PCB degradation under in situ conditions.  Wat. Res. 47(1): 141-152. [ABSTRACT]

Oza, J.P., K.R. Sowers and J.J. Perona. 2012. Linking energy production and protein synthesis in hydrogenotrophic methanogens.  Biochem. 51: 2378-2389. [ABSTRACT]


Kjellerup, B.V., P. Paul, U. Ghosh, H.D. May, K.R. Sowers. 2012. Aroclor 1260 contaminated soils show spatial variability of dechlorinating bacteria and PCB reducing activities.  Appl. Environ. Soil  Microbiol.  Article ID 584970: 1-11.  [ABSTRACT]

Anderson, K. and K.R. Sowers.  2012.  Desiccation as a Long-Term Survival Mechanism for the archaeon Methanosarcina barkeriAppl. Environ. Microbiol.  78: 1473-1479.  [ABSTRACT]

Payne, R.B., C.L. Chun, H.D. May, K.R. Sowers.  2011.  Enhanced reductive dechlorination of polychlorinated biphenyl impacted sediment by bioaugmentation with a dehalorespiring bacterium.  Env. Sci & Tech. 45 (20), pp 8772–8779.  [ABSTRACT]

Menezes, S., K. Gaston, K. Krivos, E.E. Apolinario, N.O. Reich, K.R. Sowers, P.A. Limbach, J.J. Perona.  2011.  Formation of m2G6 in Methanocaldococcus jannaschii tRNA catalyzed by the novel methyltransferase Trm14.  Nucl. Acids Res.  39(17): 7641-7655.  [ABSTRACT]

Fagervold, Sonja K., Joy E. M. Watts Harold D. May and Kevin R. Sowers.  2011.  Bioaugmentation with dechlorinating microorganisms influences the pathways and rates of PCB dechlorination in sediment microcosms.  Wat. Res.  45: 3899-3907.  [ABSTRACT]

Sowers, K.R.  2011.  Methanogenesis. In: T. Schmidt & M. Schaechter (eds.), Topics in Ecological & Environmental Microbiology. Elsevier, Inc. ISBN 13: 978-0-12-383878-0.  

Chen, Y., Apolinario, E., Brachova, L., Kelman, Z., Li, Z., Nikolau, B. J., Showman, L., Sowers, K., and Orban, J.  2010.  An integrated approach to accurate functional annotation of putative enzymes in the methanogen M. acetivoransBMC Genomics 12(Suppl 1): S7.  [ABSTRACT]

Park J.W., Krumins V., Kjellerup B.V., Fennell D.E., Rodenburg L.A., Sowers K.R, Kerkhof L.J., Häggblom M.M.  2010.  The effect of co-substrate activation on indigenous and bioaugmented PCB dechlorinating bacterial communities in sediment microcosms.  Appl. Microbiol. Biotechnol. 89: 2005-2017 [ABSTRACT]

Anderson, K.L., E.E. Apolinario, S.R. MacAuley, and K.R. Sowers.  2009.  Localization of a regulatory region within the 5’ untranslated leader region of an archaeal CO dehydrogenase/acetyl-coenzyme synthase.  J. Bacteriol. 191(22): 7123-7128  [ABSTRACT].  

Allen,  M.A., F.M. Lauro, T.J. Williams, D. Burg, K.S. Siddiqui, D. De Francisci, K.W.Y. Chong, O. Pilak, H.H. Chew, M.Z. De Maere, L. Ting, M. Katrib, C. Ng, K.R. Sowers, M.Y. Galperin, I.J. Anderson, N. Ivanova, E. Dalin, M. Martinez, A. Lapidus, L. Hauser, M. Land, T. Thomas, and R. Cavicchioli.  2009.  The genome sequence of the psychrophilic archaeon, Methanococcoides burtonii: the role of genome evolution in cold adaptation.  ISME J. 3: 1012-1035 [ABSTRACT]

Kjellerup, B.V., Kjeldsen, K., Lopes, F., Abilggaard, L., Ingvorsen, K., Frřlund, B., Sowers, K.R. and Nielsen, P.H.  2009.  Biocorrosion and biofilm formation in a nutrient limited heating system subjected to alternating microaerophilic conditions.  Biofouling. 25(8): 727-737.

MacAuley, S.R.,  S.A. Zimmerman, E.E. Apolinario, C. Evilia, Y.-M. Hou, J.G. Ferry, K.R. Sowers.  2009.  The Archetype g-Class Carbonic Anhydrase (Cam) Contains Iron when Synthesized in vivo in Methanosarcina acetivorans.  Biochemistry 48(5): 817-9 [ABSTRACT]

Tal, Y., H.J. Schreier, K.R. Sowers, J.D. Stubblefield, A.R. Place, and Y. Zohar.  2009.  Environmentally Sustainable, Fully Contained Marine Aquaculture.  Aquaculture 286: 28-35.  [ABSTRACT]. 

Sowers, K.R.  2009.  Methanogenesis. In: Schaechter, Lederberg, Alexander, Haselkorn, Ingraham, Baross, Schmidt, Laskin, Hopwood, Summers, Baulcombe, Levin, White, Fierer, Baldauf (eds.), Encylopedia of Microbiology, 3rd edition. Elsevier, Inc. ISBN: 978-0-12-373944-5.   

Kjellerup, B., Olesen, B.H., Sowers, K. R., Nielsen, P., Nielsen, J.  2008.  In situ detection of bacteria involved in cathodic depolarization and stainless steel surface corrosion using microautoradiography.  J. Appl. Microbiol.  105: 2231–2238.  [ABSTRACT]. 

Mirzoyan, N., S. Parnes, A. Singer, Y. Tal, K. Sowers and A. Gross.  2008.  Quality of brackish water aquaculture sludge and its suitability for anaerobic digestion and methane production in an upflow anaerobic sludge blanket (UASB) reactor.  Aquaculture  279: 35-41[ABSTRACT].

May, H.D., G. S. Miller, B.V. Kjellerup, K.R. Sowers 2008.  Dehalorespiration with Polychlorinated Biphenyls by an Anaerobic Ultramicrobacterium.  Appl. Environ. Microbiol. 74: 2089-2094 [ABSTRACT].

Kjellerup, B.V., X. Sun, U. Ghosh, H.D. May and K.R. Sowers.  2008.  Site specific microbial communities in three PCB-impacted sediments are associated with different in situ dechlorinating activities.  Environ. Microbiol. 10: 1296-1309 [ABSTRACT].

Fagervold, S.K., H.D. May and K.R. Sowers.  2007.  Microbial reductive dechlorination of Aroclor 1260 in Baltimore Harbor sediment microcosms is catalyzed by three phylotypes within the Chloroflexi.  Appl. Environ. Microbiol. 73: 3009-3018 [ABSTRACT].

Sowers, K.R., S. DasSarma and P. Blum.  2007.  Gene transfer in Archaea.  In: C. A. Reddy, T. J. Beveridge, J. A. Breznak, G. A. Marzluf, and T. M. Schmidt (ed.), Methods for General and Molecular Microbiology.  American Society for Microbiology, Washington, D. C.  ISBN: 978-1-55581-223-2. 

Sowers, K.R. and K. Anderson.  2007.  Molecular Genetics of Archaea.  In: R. Cavicchioli (ed.), Archaea: Molecular Cell Biology.  American Society for Microbiology, Washington, D. C., pp. 463-477.  ISBN: 978-1-55581-391-8

D.L. Maeder, I. Anderson, T. Brettin, D. Bruce, P. Gilna, C. S. Han, A. Lapidus, W.W. Metcalf, E. Saunders, R. Tapia, and K.R. Sowers.  2006.  The Methanosarcina barkeri genome: comparative analysis with Methanosarcina acetivorans and Methanosarcina mazei reveals extensive rearrangement within methanosarcinal genomes.  J. Bacteriol. 188: 7922-793 [ABSTRACT].

H.D. May, L.A. Cutter, G.S. Miller, C.E. Milliken, J.E.M. Watts, and K.R. Sowers.  2006.  Stimulatory and Inhibitory Effects of Organohalides on the Dehalogenating Activities of PCB-Dechlorinating Bacterium o-17.  Environ. Sci Technol. 40: 5704 -5709 [ABSTRACT].

Reid, I.N., W.B. Sparks, S. Lubow, M. McGrath, M. Livio, J. Valenti, K.R. Sowers, H.D. Shukla, S. MacAuley, T. Miller, R. Suvanasuthi, R. Belas, A. Colman, F.T. Robb, P. DasSarma, J.A. Muller, J.A. Coker, R. Cavicchioli, F. Chen, S. DasSarma. 2006.  Terrestrial models for extraterrestrial life: methanogens and halophiles at Martian temperatures. Int. J. Astrobiol. 5: 89-97. [ABSTRACT] 

Kjellerup, B.V., G. Gudmonsson, K.R. Sowers, P.H. Nielsen.  2006.  Evaluation of Analytical Methods for Analyzing the Distribution of Biofilm and Active Bacteria in a Commercial Heating System. Biofouling 22: 145-151 [ABSTRACT].

Sowers, K.R. and J.E.M. Watts.  2006.  The study of strictly anaerobic microorganisms.  In: F. A. Rainey and A. Oren (ed.),  Methods in Microbiology - Extremophiles, v. 35. Elsevier/Academic Press, Oxford, pp. 739-764.  ISBN: 0-12-521537-1 [ABSTRACT].


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