In response to compatible rhizobia, leguminous plants develop unique plant organs, root nodules, in which rhizobia fix nitrogen into ammonia. During nodule invasion, the rhizobia gain access to newly divided cells, the nodule primordia, in the root inner cortex through plant-derived cellulose tubes called infection threads. Infection threads begin in curled root hairs and bring rhizobia into the root crossing several cell layers in the process. Ultimately the rhizobia are deposited within nodule primordium cells through a process resembling endocytosis. Plant host mechanisms underlying the formation and regulation of the invasion process are not understood. To identify and clone plant genes required for nodule invasion, recent efforts have focused on Medicago truncatula. In a collaborative effort the nodulation defect in the lin (lumpy infections) mutant was characterized. From an EMS-mutagenized population of M. truncatula, two non-allelic mutants nip (numerous infections with polyphenolics) and sli (sluggish infections) were identified with defects in nodule invasion. Infection threads were found to proliferate abnormally in the nip mutant nodules with only very rare deposition of rhizobia within plant host cells. nip nodules were found to accumulate polyphenolic compounds, indicative of a host defense response. Interestingly, nip was also found to have defective lateral root …

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 …

Methods to determine genetic diversity and relatedness within populations are essential tools for proper wildlife management. Today the approach of choice is polymerase chain reaction-based microsatellite analysis. Seven new polymorphic loci were isolated from a microsatellite-enriched Caribbean flamingo genomic library and used to characterize survey populations of Caribbean and African greater flamingos. In addition, four of these loci were used to verify parentage relationships within a captive-breeding population of African greater flamingos. Parentage predictions based upon gamekeeper observations of breeding and nesting did not always agree with genetic-based parentage analyses of the nine suggested family groups. Four family groups were supported (groups I, II, III and VI) by there results. However, an analysis of the remaining five suggested groups, with a total of eight offspring/dam and eight offspring/sire suggested relationships, yielded seven exclusions of the suggested dam and six exclusions of the suggested sire. This put the overall suggested dam exclusion rate at 35% and exclusion rate for suggested sires at 29%. Although the keeper observation data for our family groups must be considered a variable of concern at this time, these findings are certainly suggestive that more carefully controlled studies may reveal that flamingos are not monogamous as long …

Flamingo species generate tremendous interest whether they are small captive groups or wild populations numbering in the thousands. Genetic pedigrees are invaluable for maintaining maximum genetic diversity in captive, as well as wild, populations. However, presently there is a general lack of genetic data for flamingo populations. Microsatellites are loci composed of 2-6 base pair tandem repeats, scattered throughout higher eukaryotic genomes, often exhibiting high levels of polymorphism and heterozygosity. These loci are thus important genetic markers for identity, parentage and population studies. Here, six microsatellite loci were isolated from a microsatellite-enriched Caribbean flamingo partial genomic library. Two are compound complex repeats and four are perfect trinucleotide repeats. Each locus was amplified from Caribbean, African greater, Chilean and lesser flamingo genomic DNAs. Heterozygosity frequencies were calculated for Caribbean (range 0.12-0.90) and African greater flamingos (range 0.23-0.94) loci. All six microsatellite loci were found to be in Hardy-Weinberg equilibrium and linkage disequilibrium analyses did not suggest linkage for any pair of two greater flamingo subspecies (African and Caribbean) loci. At least five of the loci also exhibit polymorphism in Chilean and lesser flamingos, but due to small sample numbers, relevant allele/heterozygosity frequency calculations could not be estimated. Nucleotide sequence comparisons of …