Natural transformation is the process by which cells take up DNA from the surrounding medium under physiological conditions, altering the genotype in a heritable fashion. This occurs without chemical or physical treatment of the cells. Certain Acinetobacter strains exhibit a strong tendency to incorporate homologous DNA into their chromosomes by natural transformation. Transformation in Acinetobacter exhibits several unique properties that indicate this system's superiority as a model for transformation studies or studies which benefit from the use of transformation as an experimental method of gene manipulation. Pseudomonas putida is the natural host of TOL plasmids, ranging between 50 kbp and 300 kbp in size and encoding genes for the catabolism of toluene, meta-toluate, and xylene. These very large, single-copy plasmids are difficult to isolate, manipulate, or modify in vitro. In this study, the TOL plasmid pDKR1 was introduced into Acinetobacter calcoaceticus strains and genetically engineered utilizing natural transformation as part of the process. Following engineering by transformation, the recombinant DNA molecule was returned to the native genetic background of the original host P. putida strain. Specific parameters for the successful manipulation of large plasmids by natural transformation in Acinetobacter were identified and are outlined. The effects of growth phase, total …

Polyunsaturated fatty acids are major structural components of plant chloroplast and endoplasmic reticulum membranes. Two fatty acid desaturases (designated FAD2 and FAD3) desaturate 75% of the fatty acids in the endoplasmic reticulum. The w -6 fatty acid desaturase (FAD2) may be responsible for cold acclimation response, since polyunsaturated phospholipids are important in helping maintain plant viability at lowered temperatures. To study regulation of FAD2 gene expression in cotton, a FAD2 gene was isolated from two genomic libraries using an Arabidopsis FAD2 hybridization probe and a cotton FAD2 5¢ -flanking region gene-specific probe, respectively. A cotton FAD2 gene was found to be in two overlapping genomic clones by physical mapping and DNA sequencing. The cloned DNA fragments are identical in size to cotton FAD2 genomic DNA fragments shown by genomic blot hybridization. The cotton FAD2 coding region has 1,155 bp with no introns and would encode a putative polypeptide of 384 amino acids. The cotton FAD2 enzyme has a high identity of 75% with other plant FAD2 enzymes. The enzyme has three histidine-rich motifs that are conserved in all plant membrane desaturases. These histidine boxes may be the iron-binding domains for reduction of oxygen during desaturation. To confirm that this FAD2 …

The most apparent symptom of boron deficiency in higher plants is a cessation of growth. Deficiency causes a reduction in ascorbate concentration and the absorption of nutrient ions. Addition of ascorbate temporarily relieves deficiency symptoms. In boron sufficient plants the addition of ascorbate to media causes an increased uptake of nutrients. In an attempt to discover if ascorbate addition to deficient plants causes increased ion uptake, radish plants were grown hydroponically in four different strengths of boron solution. A colorimetric assay for phosphorus was performed both before and after supplementation. Results, however, were inconclusive.

The enzyme, aspartate transcarbamoylase (ATCase) from Moraxella (Branhamella) catarrhalis, has been purified. The holoenzyme has a molecular mass of approximately 510kDa, harbors predominantly positive charges and is hydrophobic in nature. The holoenzyme possesses two subunits, a smaller one of 40 kDa and a larger one of 45 kDa. A third polypeptide has been found to contribute to the overall enzymatic activity, having an approximate mass of 55 kDa. The ATCase purification included the generation of cell-free extract, streptomycin sulfate cut, 60 °C heat step, ammonium sulfate cut, dialysis and ion, gel-filtration and hydrophobic interaction chromatography. The enzyme's performance throughout purification steps was analyzed on activity and SDS-PAGE gradient gels. Its enzymatic, specific activities, yield and fold purification, were also determined.

A cotton PATE cDNA clone has a 1.7-kb insert with an coding region for 410 amino acids, lacking codons for the three N-terminal amino acids. The predicted amino acid sequence of the PATE preprotein has a characteristic stromal-targeting domain and a 63% identity to the Arabidopsis FatB1 thioesterase sequence. A cotton genomic clone containing a 17.4-kb DNA segment was found to encompass a palmitoyl-ACP thioesterase (FatB1) gene. The gene spans 3.6 kb with six exons and five introns. The six exons are identical in nucleotide sequence to the open reading frame of the corresponding cDNA, and would encode a preprotein of 413 amino acids. The preprotein is identified as a FatB thioesterase from its deduced amino acid sequence similarity to those of other FatB thioesterase preproteins. A 5'-flanking region of 914 bp was sequenced, with the potential promoter/enhancer elements including basic helix-loop-helix elements (E box). Alkaline blot hybridization of cotton genomic DNA suggests the presence at least two FatB1 thioesterase genes in cotton. Four plasmid constructs for both constitutive and seed-specific anti-sense RNA suppression and gene-transgene co- suppression of PATE gene expression were successfully generated. Two overlapping cotton genomic clones were found to encompass a Δ-12 fatty acid desaturase (FAD2-3) …

Roseate spoonbills are colonial nesting birds with breeding grounds extending from the United States Gulf coast to the pampas of Argentina. The U.S. population suffered a severe bottleneck from 1890 to 1920. The population's recovery was slow and partially credited to migrations from Mexican rookeries, but a gene pool reduction would be expected. Five polymorphic Spoonbill autosomal short tandem repeat (STR) loci [three (GAT)n, one (AAAG)n and one (GT)n] and one Z/W-linked microsatellite exhibiting sex-specific dimorphism were isolated and characterized. The Z/W-linked STR locus accurately confirmed the sex of each bird. Allelic profiles for 51 spoonbills obtained from Dallas (Texas), Fort Worth (Texas) and Sedgwick County (Kansas) zoos revealed a non-continuous distribution of allele frequencies, consistent with the effects of a population bottleneck. Allelic frequencies also differed significantly between the isolated zoo populations. Although extra-pair copulations were suspected and difficult to document, zoos commonly used observational studies of mating pairs to determine familial relationships among adults and offspring. STR parentage analysis of recorded family relationships excluded one or both parents in 10/25 cases studied and it was further possible to identify alternative likely parents in each case. Mistaken familial relationships quickly lead to the loss of genetic variability in captive …

Large amounts of industrial fertilizers are used to maximize crop yields. Unfortunately, they are not completely consumed by plants; consequently, this leads to soil pollution and negative effects on aquatic systems. An alternative to industrial fertilizers can be found in legume plants that provide a nitrogen source that is not harmful for the environment. Legume plants, through their symbiosis with soil bacteria called rhizobia, are able to reduce atmospheric nitrogen into ammonia, a biological nitrogen source. Establishment of the symbiosis requires communication on the molecular level between the two symbionts, which leads to changes on the cellular level and ultimately results in nitrogen-fixing nodule development. Inside the nodules hypoxic environment, the bacterial enzyme nitrogenase reduces atmospheric nitrogen to ammonia. Medicago truncatula is the model legume plant that is used to study symbiosis with mycorrhiza and with the bacteria Sinorhizobium meliloti. The focus of this work is the M. truncatula nodulation mutant nip (numerous infections and polyphenolics). The NIP gene plays a role in the formation and differentiation of nodules, and development of lateral roots. Studying this mutant will contribute knowledge to understanding the plant response to infection and how the invasion by rhizobia is regulated. Previous genetic mapping placed NIP …

The expression of two cotton osmotin genes was evaluated in terms of the mRNA and protein expression patterns in response to chemical inducers such as ethylene, hydrogen peroxide, and sodium chloride. Reverse transcriptase-polymerase chain reactions (RT-PCR) indicated that osmotin mRNAs are expressed constitutively in root tissues of cotton plants, and that they are rapidly induced in leaf and stem tissues upon ethylene treatment. Real time RT-PCR indicated that osmotin transcript levels were induced 2 to 4 h after treatment with ethephon. The osmotin mRNA levels appear to increase 12 h after treatment, decrease, and then increase again. The osmotin protein expression patterns were analyzed in Western blot analyses using an anti-osmotin antibody preparation. A 24-KDa protein band was detected from cotton plants treated with the inducers. The 24-KDa osmotin proteins were induced 4 h after treatment with ethephon, while down-regulated 96 h after treatment. Multiple osmotin isoforms were observed to be induced in cotton plants upon treatment with ethephon by two-dimensional gel electrophoresis. One goal of this dissertation research was to genetically engineer two cotton osmotin genes to routinely overproduce their antifungal proteins in transgenic Arabidopsis and cotton plants as a natural defense against fungal infections, using co-cultivation with Agrobacterium …

To further facilitate mitochondrial DNA (mtDNA) sequence analysis for human identity testing, a better understanding of its mutation rate is needed. Prior to the middle 1990's the mutation rate applied to a forensic or evolutionary analysis was determined by phylogenetic means, This method involved calculating genetic distances as determined by amino acid or DNA sequence variability within or between species. The mutation rate as determined by this method ranged from 0.025-0.26 nucleotide substitutions/ site/ myr (million years). With the recent advent of mtDNA analysis as a tool in human identity testing an increased number of observations have recently come to light calling into question the mutation rate derived from the phylogenetic method. The mutation rate as observed from forensic analysis appears to be much higher than that calculated phylogenetically. This is an area that needs to be resolved in human identity testing. Mutations that occur within a maternal lineage can lead to a possible false exclusion of an individual as belonging to that lineage. A greater understanding of the actual rate of mutation within a given maternal lineage can assist in determining criteria for including or excluding individuals as belonging to that lineage. The method used to assess the mutation …

The soil-nematode Caenorhabditis elegans survives oxygen deprivation (anoxia < 0.001 kPa of O2, 0% O2) by entering into a state of suspended animation during which cell cycle progression at interphase, prophase and metaphase stage of mitosis is arrested. I conducted cell biological characterization of embryos exposed to various anoxia exposure times, to demonstrate the requirement and functional role of spindle checkpoint gene san-1 during brief anoxia exposure. I conducted a synthetic lethal screen, which has identified genetic interactions between san-1, other spindle checkpoint genes, and the kinetochore gene hcp-1. Furthermore, I investigated the genetic and cellular mechanisms involved in anoxia-induced prophase arrest, a hallmark of which includes chromosomes docked at the nuclear membrane. First, I conducted in vivo analysis of embryos carried inside the uterus of an adult and exposed to anoxic conditions. These studies demonstrated that anoxia exposure prevents nuclear envelope breakdown (NEBD) in prophase blastomeres. Second, I exposed C. elegans embryos to other conditions of mitotic stress such as microtubule depolymerizing agent nocodazole and mitochondrial inhibitor sodium azide. Results demonstrate that NEBD and chromosome docking are independent of microtubule function. Additionally, unlike anoxia, exposure to sodium azide causes chromosome docking in prophase blastomeres but severely affects embryonic viability. …

Utilization of cyanide as the sole nitrogen source by Pseudomonas fluorescens NCIMB 11764 (Pf11764) occurs via oxidative conversion to carbon dioxide and ammonia, the latter satisfying the nitrogen requirement. Substrate attack is initiated oxygenolytically by an enzyme referred to as cyanide oxygenase (CNO), which exhibits properties of a pterin-dependent hydroxylase. The pterin requirement for Pf11764 CNO was satisfied by supplying either the fully (tetrahydro) or partially (dihydro) reduced forms of various pterin compounds at catalytic concentrations (0.5 µM). These compounds included, for example, biopterin, monapterin and neopterin, all of which were also identified in cell extracts. A related CNO-mediated mechanism of cyanide utilization was identified in cyanide-degrading P. putida BCN3. This conclusion was based on (i) the recovery of CO2 and NH3 as enzymatic reaction products, (ii) the dependency of substrate conversion on both O2 and NADH, and (iiii) utilization of cyanide, O2 and NADH in a 1:1:1 reaction stoichiometry. In contrast to findings reported for Pf11764, it was not possible to demonstrate a need for exogenously added pterin as a cofactor for the PpBCN3 enzyme system. However, results which showed that cells of PpBCN3 contained approximately seven times the amount of pterin as Pf11764 (of which a significant portion …

The pyrimidine biosynthetic pathway is an essential pathway for most organisms. Previous research on the pyrimidine pathway in Pseudomonas aeruginosa (PAO1) has shown that a block in the third step of the pathway resulted in both a requirement for exogenous pyrimidines and decreased ability to produce virulence factors. In this work an organism with a mutation in the second step of the pathway, aspartate transcarbamoylase (ATCase), was created. Assays for pyrimidine intermediates, and virulence factors were performed. Results showed that the production of pigments, haemolysin, and rhamnolipids were significantly decreased from PAO1. Elastase and casein protease production were also moderately decreased. In the Caenorhabditis elegans infection model the nematodes fed the ATCase mutant had increased mortality, as compared to nematodes fed wild type bacteria. These findings lend support to the hypothesis that changes in the pyrimidine biosynthetic pathway contribute to the organism's ability to effect pathogenicity.

Burkholderia cepacia is a common soil bacterium of significance in agriculture and bioremediation. B. cepacia is also an opportunistic pathogen of humans causing highly communicable pulmonary infections in cystic fibrosis and immunocompromized patients. The pyrB gene encoding ATCase was cloned and ATCase was purified by the glutathione S-transferase gene fusion system. The ATCase in B. cepacia has been previously classified as a class A enzyme by Bethell and Jones. ATCase activity gels showed that B. cepacia contained a holoenzyme pyrBC complex of 550 kDa comprised of 47 kDa pyrB and 45 kDa pyrC subunits. In the course of purifying the enzyme, trimeric subunits of 140 kDa and 120 kDa were observed as well as a unique proteolysis of the enzyme. The 47 kDa ATCase subunits were cleaved to 40 kDa proteins, which still demonstrated high activity as trimers. The proteolysis site is between Ser74 and Val75 residues. To confirm this, we converted the Ser74 residue to an Ala and to an Arg by site-directed mutagenesis. After this primary sequence changed, the proteolysis of ATCase was not observed. To further investigate the characteristics of B. cepacia pyrB gene, a pyrB knock-out (pyrB-) was constructed by in vitro mutagenesis. In the assay, …

The regulatory gene for pyrimidine biosynthesis has been identified and designated pyrR. The pyrR gene product was purified to homogeneity and found to have a monomeric molecular mass of 19 kDa. The pyrR gene is located directly upstream of the pyrBC' genes in the pyrRBC' operon. Insertional mutagenesis of pyrR led to a 50- 70% decrease in the expression of pyrBC', pyrD, pyrE and pyrF while pyrC was unchanged. This suggests that PyrR is a positive activator. The upstream regions of the pyrD, pyrE and pyrF genes contain a common conserved 9 bp sequence to which the purified PyrR protein is proposed to bind. This consensus sequence is absent in pyrC but is present, as an imperfect inverted repeat separated by 11 bp, within the promoter region of pyrR. Gel retardation assays using upstream DNA fragments proved PyrR binds to the DNA of pyrD, pyrE, pyrF as well as pyrR. This suggests that expression of pyrR is autoregulated; moreover, a stable stem-loop structure was determined in the pyrR promoter region such that the SD sequence and the translation start codon for pyrR is sequestered. β-galactosidase activity from transcriptional pyrR::lacZ fusion assays, showed a two-fold in increase when expressed in a …

The Medicago truncatula NIP gene is located on M. truncatula Linkage Group 1. Informative recombinants showed crossovers that localize the NIP gene between markers 146O17 and 23C16D. Marker 164N9 co-segregates with the NIP gene, and the location of marker 164N9 is between markers 146O17 and 23C16D. Based upon data from the Medicago genome sequencing project, a subset of the model legume Medicago truncatula bacterial artificial chromosomes (BACs) were used to create a physical map on the DNA in this genetic internal. BACs near the potential NIP gene location near marker 164N9 were identified, and used in experiments to predict the physical map by a BAC-by-BAC strategy. Using marker 164N9 as a center point, and chromosome walking outward, the physical map toward markers 146O17 and 23C16D was built. The chromosome walk consisted of a virtual walk, made with existing sequence of BACs from the Medicago genome project, hybridizations to filters containing BAC DNA, and PCR reactions to confirm that predicted overlapping BACs contained DNA that yielded similar PCR products. In addition, the primers which are made for physical mapping via PCR could be good genetic markers helpful in discovering the location of the NIP gene. As a result of efforts repotted …

The primary objectives of this project were: 1. to develop improved methods for extraction of DNA from human skeletal remains, 2. to improve STR profiling success of low-copy DNA samples by employing whole genome amplification to amplify the total pool of DNA prior to STR analysis, and 3. to improve STR profiling success of damaged DNA templates by using DNA repair enzymes to reduce the number/severity of lesions that interfere with STR profiling. The data from this study support the following conclusions. Inhibitory compounds must be removed prior to enzymatic amplification; either during bone section pretreatment or by the DNA extraction method. Overall, bleach outperformed UV as a pretreatment and DNA extraction using silica outperformed microconcentration and organic extraction. DNA repair with PreCR™ A outperformed both whole genome amplification and repair with PreCR™ T6. Superior DNA extraction results were achieved using the A6 PMB columns (20 ml capacity column with 6 layers of type A glass fiber filter), and DNA repair with PreCR™ A led to an overall improvement in profile quality in most cases, although whole genome amplification was unsuccessful. Rapid, robust DNA isolation, successful amplification of loci from the sample-derived DNA pool, and an elimination of DNA damage …

Campylobacter organisms are the most commonly reported bacterial causes of foodborne infection in the world, with Campylobacter jejuni and Campylobacter coli responsible for over 99% of reported infections. Traditionally, Campylobacter species detection is an arduous process, requiring a special incubation environment as well as specific growth media for an extended growth period. The development of a rapid and reliable diagnostic tool for the detection of Campylobacter species would be a valuable aid to the medical diagnostic decision process, especially to rule out Campylobacter infection during the enteric pre-surgical time period. Improved patient outcomes would result if this rapid assay could reduce the number of enteric surgeries. Assays performed during this dissertation project have demonstrated that both SYBR® green and hydrolysis probe assays targeting an 84 nucleotide portion of cadF, a fibronectin-binding gene of Campylobacter jejuni and Campylobacter coli, were able to detect from 101 to 108 copies of organism from stool specimens, did not detect nonspecific targets, and exhibited a coefficient of variation (CV) of 1.1% or less. Analytical validation of sensitivity, specificity and precision, successfully performed in these studies, warrants additional clinical validation of these assays.

Fatty acid desaturase 2 (FAD2) enzymes are phosphatidylcholine desaturases occurring as integral membrane proteins in the endoplasmic reticulum membrane and convert monounsaturated oleic acid into polyunsaturated linoleic acid. The major objective of this research was to study the expression and function of two cotton FAD2 genes (the FAD2-3 and FAD2-4 genes) and their possible role in plant sensitivity to environmental stress, since plants may increase the polyunsaturated phospholipids in membranes under environmental stress events, such as low temperature and osmotic stress. Two FAD2 cDNA clones corresponding to the two FAD2 genes have been isolated from a cotton cDNA library, indicating both genes are truly expressed in cotton. Model yeast cells transformed with two cotton FAD2 genes were used to study the chilling sensitivity, ethanol tolerance, and growth rate of yeast cells. The expression patterns of the two FAD2 genes were analyzed by reverse transcription polymerase chain reactions (RT-PCR) and Western blot analyses in cotton plants under different treatment conditions. The coding regions of both FAD2 genes were inserted downstream from the CaMV 35S promoter in the pMDC gateway binary vector system. Five different FAD2/pMDC constructs were transformed into the Arabidopsis fad2 knockout mutant background, and multiple potential transgenic Arabidopsis plant …

Pseudomonas fluorescens NCIMB 11764 (Pf11764) is uniquely able to grow on the poison cyanide as its sole nitrogen source. It does so by converting cyanide oxidatively to carbon dioxide and ammonia, the latter being assimilated into cellular molecules. This requires a complex enzymatic machinery that includes nitrilase and oxygenase enzymes the nature of which are not well understood. In the course of a proteomics analysis aimed at achieving a better understanding of the proteins that may be required for cyanide degradation by Pf11764, an unknown protein of 17.8 kDa was detected in cells exposed to cyanide. Analysis of this protein by ESI-coupled mass spectrometry and bioinformatics searches gave evidence of strong homology with a protein (Hyp1) of unknown function (hypothetical) present in the bacterium Photorhabdus luminescens subsp. laumondii TTO1 (locus plu_1232). A search of available microbial genomes revealed a number of Hyp1 orthologs the genes of which are found in a conserved gene cluster known as Nit1C. Independent studies revealed that in addition to Hyp1, Pf11764 possesses a gene (nit) specifying a nitrilase enzyme whose closest homologue is a nitrilase found in Nit1C gene clusters (77% amino acid identity). DNA sequence analysis has further revealed that indeed, hyp1Pf11764 and nitPf11764 …

N-Acylethanolamines (NAEs) are bioactive acylamides that are present in a wide range of organisms. Because NAE levels in seeds decline during imbibition similar to ABA, a physiological role was predicted for these metabolites in Arabidopsis thaliana seed germination and seedling development. There is also a corresponding increase of AtFAAH (fatty acid amide hydrolase), transcript levels and activity, which metabolizes NAE to ethanolamine and free fatty acids. Based on whole genome microarray studies it was determined that a number of up-regulated genes that were responsive to NAE were also ABA responsive. NAE induced gene expression in these ABA responsive genes without elevating endogenous levels of ABA. It was also determined that many of these NAE/ABA responsive genes were associated with an ABA induced secondary growth arrest, including ABI3. ABI3 is a transcription factor that regulates the transition from embryo to seedling growth, the analysis of transcript levels in NAE treated seedlings revealed a dose dependent, inverse relationship between ABI3 transcript levels and growth, high ABI3 transcript levels were associated with growth inhibition. Similar to ABA, NAE negatively regulated seedling growth within a narrow window of early seedling establishment. When seedlings are exposed to NAE or ABA within the window of sensitivity, …

This thesis is a comparative study of gene arrangements in Pseudomonas species, and is organized into three major sections. The first section compares gene arrangements for different pathways in Pseudomonas aeruginosa PAO1 to determine if the gene arrangements are similar to previous studies. It also serves as a reference for pyrimidine gene arrangements in P. aeruginosa. The second part compares the physical, and genetic maps of P. aeruginosa PAO1 with the genome sequence. The final section compares pyrimidine gene arrangements in three species of Pseudomonas. Pyrimidine biosynthesis and salvage genes will be aligned for P. aeruginosa PAO1, P. putida KT2440, and P. syringae DC3000. The whole study will gives insight into gene patterns in Pseudomonas, with a focus on pyrimidine genes.

The ability to synthesize pyrimidine nucleotides is essential for most organisms. Pyrimidines are required for RNA and DNA synthesis, as well as cell wall synthesis and the metabolism of certain carbohydrates. Recent findings, however, indicate that the pyrimidine biosynthetic pathway and its intermediates maybe more important for bacterial metabolism than originally thought. Maksimova et al., 1994, reported that a P. putida M, pyrimidine auxotroph in the third step of the pathway, dihydroorotase (DHOase), failed to produce the siderophore pyoverdin. We created a PAO1 DHOase pyrimidine auxotroph to determine if this was also true for P. aeruginosa. Creation of this mutant was a two-step process, as P. aeruginosa has two pyrC genes (pyrC and pyrC2), both of which encode active DHOase enzymes. The pyrC gene was inactivated by gene replacement with a truncated form of the gene. Next, the pyrC2 gene was insertionally inactivated with the aacC1 gentamicin resistance gene, isolated from pCGMW. The resulting pyrimidine auxotroph produced significantly less pyoverdin than did the wild type. In addition, the mutant produced 40% less of the phenazine antibiotic, pyocyanin, than did the wild type. As both of these compounds have been reported to be vital to the virulence response of P. aeruginosa, …

Three overlapping genomic clones covering 29.0 kilobases of cotton DNA were found to encompass a cluster of two presumptive osmotin genes (OSMI and OSMII) and two osmotin pseudogenes (OSMIII and OSMIV). A segment of 16,007 basepairs of genomic DNA was sequenced from the overlapping genomic clones (GenBank Accessions AY303690 and AF304007). The two cotton osmotin genes were found to have open reading frames of 729 basepairs without any introns, and would encode presumptive osmotin preproteins of 242 amino acids. The open reading frames of the genes are identical in sequence to two corresponding cDNA clones (GenBank Accessions AF192271 and AY301283). The two cDNA inserts are almost full-length, since one lacks codons for the four N-terminal amino acids, and the other cDNA insert lacks the coding region for the 34 N-terminal amino acids. The cotton osmotin preproteins can be identified as PR5 proteins from their similarities to the deduced amino acid sequences of other plant osmotin PR5 preproteins. The preproteins would have N-terminal signal sequences of 24 amino acids, and the mature 24 kilodalton isoforms would likely be targeted for extracellular secretion. Prospective promoter elements, including two ethylene response elements, implicated as being positive regulatory elements in the expression of a …

Previous research in our laboratory showed that when knockout mutations were created in the pyrB and pyrC genes of the pyrimidine pathway in Pseudomonas aeruginosa, not only were the resultant mutants auxotrophic for pyrimidines but they were also impaired in virulence factor production. Such a correlation had not been previously reported for P. aeruginosa, a ubiquitous opportunistic pathogen in humans. In an earlier study it was reported that mutants blocked in one of the first three enzymes of the pyrimidine pathway in the non-pathogenic strain P. putida M produced no pyoverdin pigment while mutants blocked in the later steps produced copious amounts of pigment, just like the wild type. This study probed for the same connection between pyrimidine auxotrophy and pigment production applied in P. aeruginosa. To that end a knockout mutation was created in pyrD, the fourth step in the pyrimidine pathway which encodes dihydroorotate dehydrogenase. The resulting mutant required pyrimidines for growth but produced wild type pigment levels. Since the pigment pyoverdin is a siderophore it may also be considered a virulence factor, other virulence factors were quantified in the mutant. These included casein protease, hemolysin, elastase, swimming, swarming and twitching motility, and iron binding capacity. In all …