← All People

Dr. Leland S. Pierson III

Pierson III, Dr. Leland S.
Dr. Leland S. Pierson III
Professor & Head
120A LF Peterson
Undergraduate Education
B.A. Microbiology, University of California, Davis
Graduate Education
Ph.D. Microbiology, Washington State University

Research Emphasis:

1. Secondary metabolite production in beneficial bacteria.

Molecular regulation and roles of phenazines (PZ). We study the regulation and function of PZs in the root-associated bacterium Pseudomonas chlororaphis strain 30-84 and the opportunistic pathogen P. aeruginosa. PZs are nitrogen containing heterocyclic compounds produced by a wide range of soil and root-associated bacteria that are required for biofilm formation and persistence in the rhizosphere. These compounds additionally inhibit the growth of several pathogenic fungi. PZ production is regulated by a complex sensory network that includes quorum sensing, positive and negative two component regulation, and post-transcriptional regulation. Ongoing work includes the generation of bacterial derivatives producing structural PZ variants and transcriptomic analyses of the mechanisms involved in PZ regulation and in elucidating the multiple roles PZs play for the producing bacterium.

2. Signaling among microbial populations in vitro and in situ.

Phenazine (PZ) production is regulated via quorum sensing which is dependent on the accumulation of diffusible microbial pheromones. Mutants defective in the production of these signals were rescued for PZ production in vitro and in situ by signals produced by another subpopulation of the wheat rhizosphere community. Additionally, we identified a second subpopulation from the wheat rhizosphere that inhibited PZ production via the production of non-AHL signals that interfered with normal quorum sensing activation of the PZ biosynthetic operon. Thus, PZ production is influenced directly by other members of the rhizosphere community. We are studying some of the negative signals produced by select rhizosphere strains both at the genetic level and are examining their effects on PZ expression by strain 30-84 on plant roots.

Current Courses:

BESC 484W. Writing-intensive Research Internships.

BESC 481C. Communication and writing course. Current topic: water

Previously Taught:
PLP428R/528R. Microbial Genetics
 (3 units). Comprehensive course covering all aspects of prokaryotic genetics, including DNA structure and function, RNA functions, transcription, translation, phage and transposon biology, gene regulation, including post-transcriptional regulation, genome sequence analysis, cloning, PCR primer design.

PLP428L/528L. Microbial Genetics Laboratory (2 units). Laboratory course incorporating actual research projects. Includes genomic and plasmid isolation, transposon mutagenesis, restriction digestion, cloning, and DNA sequence analysis.

Recent Publications

Yu JM, Wang D, Pierson LS, Pierson EA. Disruption of MiaA Provides Insights into the Regulation of Phenazine Biosynthesis under Suboptimal Growth Conditions in Pseudomonas chlororaphis 30-84. Microbiology. PMID 27926818 DOI: 10.1099/mic.0.000409.

Wang D, Yu J-M, Dorosky RJ, Pierson III LS, and EA Pierson. 2016. The phenazine 2-hydroxy-phenazine-1-carboxylic acid promotes extracellular DNA release and has broad transcriptomic consequences in Pseudomonas chlororaphis 30-84. PLOS One DOI:10.1371.

Wang D, Dorosky RJ, Han CS, Lo CC, Dichosa AE, Chain PS, Yu JM, Pierson LS 3rd, Pierson EA. 2015. Adaptation genomics of a small-colony variant in a Pseudomonas chlororaphis 30-84 biofilm.  Appl Environ Microbiol. 81:890-899.

Wang D, Han CS, Dichosa AE, Gleasner CD, Johnson SL, Daligault HE, Davenport KW, Li PE, Pierson EA, Pierson LS 3rd. 2014. Draft Genome Sequence of Enterobacter cloacae Strain S611. Genome Announc. 11;2. pii: e00710-14.

Wang D, Lee S-H, Seeve C, Yu J-M, Pierson III LS, Pierson EA. 2013. Roles of the Gac-Rsm pathway in the regulation of phenazine biosynthesis in Pseudomonas chlororaphis 30-84. Microbiology Open. doi: 10.1002/mbo3.90.

Wang D, Han C, Dichosa A, Gleasner C, Johnson S, Daligaulta H, Davenport K, Li P-E, Pierson E, and Pierson LS III. 2013. Draft Genome Sequence of Pseudomonas putida Strain S610, a Seedborne Bacterium of Wheat (genomeA01048-13). Genome Announc. 26;1(6). pii: e01048-13. doi: 10.1128/genomeA.01048-13.

Ortiz M, Neilson JW, Nelson WM, Legatzki A, Byrne A, Yu Y, Wing RA, Soderlund CA, Pryor BM, Pierson LS 3rd, Maier RM. 2013. Profiling bacterial diversity and taxonomic composition on speleothem surfaces in Kartchner Caverns, AZ. Microb Ecol. 65:371-383. doi: 10.1007/s00248-012-0143-6. Epub 2012 Dec 9.

Wang D, Seeve C, Pierson LS 3rd, Pierson EA. 2013. Transcriptome profiling reveals links between ParS/ParR, MexEF-OprN, and quorum sensing in the regulation of adaptation and virulence in Pseudomonas aeruginosa. BMC Genomics 13;14:618. doi: 10.1186/1471-2164-14-618.

Wang B, Pierson III LS, Rensing C, Gunatilaka MK, Kennedy C. 2012. NasT-mediated antitermination plays an essential role in the regulation of the assimilatory nitrate reductase operon in Azotobacter vinelandii. Appl Environ Microbiol. 2012 Jul 6. [Epub ahead of print].

Wang D, Yu JM, Pierson III LS, Pierson EA. 2012. Differential regulation of phenazine biosynthesis by RpeA and RpeB in Pseudomonas chlororaphis 30-84. Microbiology. 158:1745-57.


Loper JE, Hassan KA, Mavrodi D, Davis II EW, Lim CH, Shaffer BT, Elborne LDH, Stockwell VO, Hartney SL, Breakwell K, Henkels MD, Tetu SG, Rangel LI, Kidarsa TA, Wilson NL, van Mortel J, Song C, Blumhagen R, Radune D, Hostetler JB, Brinkac LM, Durkin AS, Kluepfel DA, Wechter WP, Anderson AJ, Kim YC, Pierson III LS, Pierson EA, Lindow SE, Raaijmakers JM, Weller DM, Thomashow LS, Allen AE, Paulsen IT. Comparative genomics of plant-associated Pseudomonas spp.: Insights into diversity and inheritance of traits involved in multitrophic interactions. PLoS Genet 8(7): e1002784. doi:10.1371/journal.pgen.10027.

Puopolo G, Raio A, Pierson LS III, Zoina A. 2011. Selection of a new Pseudomonas chlororaphis strain for the biological control of Fusarium oxysporum f. sp. radicislycopersici. Phytopathol. Mediterr. 50:228-235.

Driscoll WW, Pepper JW, Pierson LS III, Pierson EA. 2011. Spontaneous Gac mutants in Pseudomonas biological control strains: Are they cheaters or mutualists? Appl. Environ. Microbiol. 77:7227-7235.

Young Cheol Kim, Johan Leveau, Brian B. McSpadden Gardener, Elizabeth A. Pierson Leland S. Pierson III, Choong-Min Ryu. 2011. The multifactorial basis for plant health promotion by plant-associated bacteria. J. Bacteriol. 77:2113-2121.

Pierson LS 3rd, Pierson EA. 2010. Metabolism and function of phenazines in bacteria: impacts on the behavior of bacteria in the environment and biotechnological processes. Appl Microbiol Biotechnol.86:1659-1670.

Maddula VS, Pierson EA, Pierson LS III. 2008. Altering the ratio of phenazines in Pseudomonas chlororaphis (aureofaciens) strain 30-84: effects on biofilm formation and pathogen inhibition. J. Bacteriol. 190:2759-66.

Pierson, LS, III, and EA Pierson. 2007. Roles of Diffusible Signals in Communication among Plant-Associated Bacteria.  Phytopathology 97:227-232.

Maddula VSK, Zhang Z, Pierson EA, and Pierson LSIII. 2006. Quorum Sensing and Phenazines are Required for Biofilm Formation by Pseudomonas aureofaciens Strain 30-84. Microbial Ecol. 52:289-301.