Crystal Johnson headshotCrystal N. Johnson

Position: Associate Professor, Department of Environmental Sciences

Phone: 225-578-9422


Office: 2283 Energy, Coast and Environment Building

Bachelor's Degree(s): B.S. Cell and Molecular Biology, Tulane University, 1997

Ph.D.(s): Ph.D. Microbiology, University of Alabama at Birmingham, 2004


Research Interests

I am currently examining how Vibrio spp. (V. parahaemolyticus, V. vulnificus, and V. cholerae) respond to environmental cues, including sea surface temperature, salinity, chlorophyll, turbidity, suspended particulate matter, and dissolved organic carbon. It is well-established that temperature affects the levels of these naturally occurring marine bacteria (i.e., their levels are higher in warmer months and lower in cooler months), but it remains unclear what combinations of other environmental factors contribute to the variations in vibrio levels.

I am also examining the genetic relationships among pathogenic vibrios. The vast majority of the naturally occurring vibrios are non-pathogenic, but almost all of the vibrios isolated from human illnesses contain some pathogenicity factor (such as a hemolysin or a urease). Little is known about the small subpopulation of environmental vibrios that contain these pathogenicity factors. Thus, I am using phylogenetic typing [Rep-PCR, multilocus sequence typing (MLST)] to identify the relationships among the potential pathogens found in water, oysters, and sediment, and also their relationship to those pathogens that turn up in humans.
I am interested in a more recently described pathogenicity factor in vibrios called the Type III Secretion System (TTSS). TTSSs work by injecting effector proteins into eukaryotic cells that interfere with host cell signaling cascades and their ability to mount an immune response to fight off vibrio infections. I have also recently developed an interest in avian microbiology and currently seek collaborations in this area.

I also have a strong commitment to outreach. As a component of my current NSF funding, I established the Summer Research Internship (SumRI), in which two high school students spend 6-8 weeks in my lab each summer doing hands-on research using vibrios that the students themselves isolate and characterize. I also enjoy speaking to the public about science, including how and why I became a scientist, general microbiology, and what my research in particular means for the general public.

Classes Taught

NSF GK-12 Summer Science Institute (2002-2004).
Teaching assistant for dental, optometry, and medical student microbiology labs (1998-2001).
Instructor (Spring 2006): Microbiology journal club.
Guest lecture, Marine Microbiology (COA 471/571): Waterborne Human Pathogens, Department of Coastal Sciences, The University of Southern Mississippi, March 2006.
Guest lecture, Special Topics in Biological Oceanography – Molecular Techniques in Marine Science (MAR 682): Marine Microbiology Methods, March 2008.
Guest lecture, Marine Microbiology (COA 471/571): Waterborne Human Pathogens, Department of Coastal Sciences, The University of Southern Mississippi, April 2008.
Special Problems: Denaturing Gradient Gel Electrophoresis Techniques (COA 792), Department of Coastal Sciences, The University of Southern Mississippi, June 2009.
Summer Research Internship (SumRI), summer 2009-2012.
ENVS Molecular Microbiology of the Environment, fall 2010.
ENVS 4500 Health Effects of Environmental Pollutants.
Introduction to Environmental Sciences, ENVS 1126, Spring 2010, Spring 2011, Spring 2012, Fall 2012, Spring 2013.
Health Effects of Environmental Pollutants, ENVS 4500, Fall 2011, Fall 2013
Biochemical and Molecular Methods in Environmental Sciences (BAMMIES), ENVS 4950 (to be developed as a full ENVS course), Fall 2010

Awards & Honors

Current Grants as PI only

2008-13: Johnson, C. N., Grimes, D. J., Bowers, J. C., Strom, M., Huq, A., Colwell, R. R., and Laws, E., Collaborative Research: Identifying Environmental Determinants Favorable for the Presence and Transmission of Pathogenic Vibrios, National Science Foundation/National Institutes of Health Ecology of Infectious Diseases, Grant # EF-1003943, award total: $2,325,000 (LSU portion $786,765)

2008-10: Lotz, J., Dillon, K., Johnson, C. N., and Grimes, D. J., US Marine Shrimp Farming Program, US Department of Agriculture Cooperative State Research, Education, and Extension Service (CSREES), award total: $98,958 (LSU portion $0)

2010-12: Johnson, C. N., King, G., and Laws, E., Gulf Oil Spill: Phytoplankton and environmental stressors as determinants of vibrio ecology, National Science Foundation RAPID, Grant #1043126, award total: $150,000 (LSU portion $150,000)

2012-14: Johnson, Role of Adjustable Longline Systems (ALS) in minimizing accumulation of potentially pathogenic vibrios in oysters, Louisiana Sea Grant, Grant #R/OVV-02, award total: $173,007 (LSU portion $173,007)

Professional Affiliations and Service Activities

1999-00: UAB Graduate School Fairs: Discussion Leader
1999-01: UAB Black Graduate Student Association, Vice President 1999-2000, President 2000-2001
2000-2001: Alabama Alliance for Graduate Education and the Professorate Graduate School Fairs: Discussion Leader
2002-2004: Gene-ius and Bio-Teach High School Programs: Lead Facilitator .
2005-07: Annual Biomedical Research Conference for Minority Students: Remote Abstracts Judge.
2007- : American Society for Microbiology (ASM) Public and Scientific Affairs Board (PSAB) Committee on Microbiological Issues Impacting Minorities (CMIIM): Ad-Hoc member, 2006-2007; Full member 2007-Present
2006-09: ASM General Meeting Minority Booth Volunteer.
2006-09: CMIIM newsletter, The Minority Microbiology Mentor: Editor-in-Chief.
2007 Marine and Estuarine Graduate Student Symposium, Gulf Coast Research Laboratory, Ocean Springs, MS: Judge, March.
2007: Microbe World interview, “Life on a Half Shell,” .
2007- : ASM Communications Committee: Member.
2007-08: Current Microbiology: Associate Editor.
2008- : NSF Graduate Research Fellowship Program, Resource Person.

Recent Publications

Chen, A. J., Hasan, N. A., Haley, B. J., Taviani, E., Tarnowski, M., Brohawn, K., Johnson, C. N., Colwell, R. R., Huq, A. (2017). Characterization of Pathogenic Vibrio parahaemolyticus from the Chesapeake Bay, Maryland. FRONTIERS IN MICROBIOLOGY, 8.

Johnson, C. N. (2015). Influence of environmental factors on Vibrio spp. in coastal ecosystems. Microbiology Spectrum.

Montazeri, N., Goettert, D., Achberger, E. C., Johnson, C. N., Prinyawiwatkul, W., Janes, M. E. (2015). Pathogenic enteric viruses and microbial indicators during secondary treatment of municipal wastewater. Applied and Environmental Microbiology, 81, 6436-6445.

Cole, K., Supan, J., Ramirez, A., Johnson, C. N. (2015). Suspension of oysters reduces the populations of Vibrio parahaemolyticus and Vibrio vulnificus. Letters in Applied Microbiology, 61, 209-213.

Selected Publications

Stephens, E., Molina, V., Cole, K., Laws, E., and Johnson, C. N., Ecological impact the Deepwater Horizon oil spill on the Vibrio parahaemolyticus type III secretion system and the vibrio community, Marine Pollution Bulletin, 75:90-97 (2013).

Johnson, C. N., Fitness factors in vibrios: a mini-review, Microbial Ecology, 65:826–851 (2013). [Invited by journal editor]

C. N. Johnson, J. C. Bowers, K. J. Griffitt, V. Molina, R. W. Clostio, S. Pei, E. Laws, R. N. Paranjpye, M. S. Strom, A. Chen, N. A. Hasan, A. Huq, N. F. Noriea III, D. J. Grimes, and R. R. Colwell, Ecology of Vibrio parahaemolyticus and Vibrio vulnificus in the Coastal and Estuarine Waters of Louisiana, Maryland, Mississippi, and Washington (United States). Applied and Environmental Microbiology, 78(20):7249–7257 (2012).

Smith, C. B., Johnson, C. N., and G. M. King, Assessment of polyaromatic hydrocarbon degradation by potentially pathogenic environmental Vibrio parahaemolyticus isolates from coastal Louisiana, USA. Marine Pollution Bulletin, 64(1):138–143 (2012).

Griffitt, K. J., Noriea, N. F., III, Johnson, C. N., and Grimes, D. J., Enumeration of Vibrio parahaemolyticus in the viable but nonculturable state using direct plate counts and recognition of individual gene fluorescence in situ hybridization.  J. Microbiol. Methods, 85(2):114-8 (2011).

Johnson, C. N., Flowers, A. R., Noriea, III, N. F., Zimmerman, A. M., Bowers, J. C., DePaola, A., and Grimes, D. J., Relationships between environmental factors and pathogenic vibrios in the northern Gulf of Mexico.  Applied and Environmental Microbiology. 76: 7076-7084 (2010).

Noriea, N. F., III, Johnson, C. N., Griffitt, K. J., and Grimes, D. J.  Distribution of type III secretion systems in Vibrio parahaemolyticus from the northern Gulf of Mexico.  Journal of Applied Microbiology, 109(3):953-62 (2010).

Grimes, D. J., Johnson, C. N., Dillon, K., Flowers, A. R., Noriea, N. F., III, and Berutti, T.  What genomic sequence information has revealed about vibrio ecology in the ocean – A review. Microbial Ecology 58:447-460 (2009).

Johnson, C. N., Flowers, A. R., Young, V. C., Gonzalez-Escalona, N., DePaola, A., and  Grimes, D. J.  Genetic relatedness among tdh+ and trh+ Vibrio parahaemolyticus cultured from Gulf of Mexico oysters (Crassostrea virginica) and surrounding water and sediment.  Microbial Ecology 57:437-443 (2009).

Johnson, C. N., Chang, Y. J., Peacock, A. D., Kline, L., Barnes, S., Ogle, J., and Grimes, D. J.  Microbial community analysis of water, foregut, and hindgut during growth of Pacific white shrimp (Litopenaeus vannamei) in closed system aquaculture.  Journal of the World Aquaculture Society, 39:251-258 (2008).

Zimmerman, A. M., DePaola, A., Bowers, J. C., Krantz, J. A., Nordstrom, J. L., Johnson, C. N., and Grimes, D. J., Variability of Total and Pathogenic Vibrio parahaemolyticus Densities in Coastal Gulf of Mexico Water and Oysters (Crassostrea virginica). Applied and Environmental Microbiology. 73: 7589-7596 (2007).

Johnson, C. N., Briles, D. E., Benjamin, W. H. Jr., Hollingshead, S. K., Waites, K. B. Relative fitness of fluoroquinolone-resistant Streptococcus pneumoniae. Emerging Infectious Diseases, 11(6):814-820 (2005).

Johnson, C. N., Molecular epidemiology and characterization of macrolide and flluoroquinolone resistance in Streptococcus pneumoniae.  Ph.D. dissertation, (2004).

Waites, K. B., Jones, K. E., Kim, K. H., Moser, S. A., Johnson, C. N., Hollingshead, S. K., Kang, E. S., Hong, K. S., Benjamin, Jr., W. H. Dissemination of macrolide-resistant Streptococcus pneumoniae isolates containing both erm(B) and mef(A) in South Korea. Journal of Clinical Microbiology.  41(12):5787-91 (2003).

Johnson, C. N., Benjamin, W., Moser, S. A., Hollingshead, S., Crain, M., Zheng, X., Nahm, M., and Waites, K. B.  Genetic relatedness of levofloxacin-nonsusceptible Streptococcus pneumoniae isolates from North America. Journal of Clinical Microbiology. 41:2458-2464 (2003).

Hilliard, N., Johnson, C. N., Armstrong, S., Quarles, S., and Waites, K. B. In vitro activities of ertapenem (MK 0826) and other antimicrobials against multi-drug resistant Streptococcus pneumoniae. International Journal of Antimicrobial Agents 20:136-140 (2002).

Chavers, S., Moser, S., Benjamin, W. H., Steinhauer, J., Smith, A. M., Johnson, C. N., Funkhouser, E., Stamm, A. and Waites, K. B. Vancomycin-resistant enterococcus: Fifteen years and counting. Journal of Hospital Infection 53:159-171 (2003). Invited Review.

Johnson, C. N., Benjamin, W. H., Gray, B. M., Crain, M. C., Edwards, K. M., and Waites, K. B. In vitro activities of ABT 773, telithromycin and eight other antimicrobials against erythromycin-resistant Streptococcus pneumoniae isolates from the respiratory tracts of children in the southeastern United States. International Journal of Antimicrobial Agents, 18:531-535 (2001).

Zheng, X., Johnson, C. N., Wang, Y., Lu, R., Yangihara, C., Hollingshead, S., Crain, M., Benjamin, W., and Waites, K.B.  Clinical isolates of Streptococcus pneumoniae resistant to levofloxacin contain mutations in both gyrA and parC genes. International Journal of Antimicrobial Agents 18:373-378 (2001).

Waites, K. B., Johnson, C. N., Gray, B. M., Edwards, K., Crain, M. C., and Benjamin, W. Use of clindamycin disks to detect macrolide resistance mediated by ermB and mefE in Streptococcus pneumoniae in children and adults. Journal of Clinical Microbiology. 38:1731-1734 (2000).