M. Persmark

Bio: M. Persmark is an academic researcher from University of California, Berkeley. The author has contributed to research in topics: Siderophore & Erwinia. The author has an hindex of 4, co-authored 4 publications receiving 191 citations.

Ferric iron uptake in Erwinia chrysanthemi mediated by chrysobactin and related catechol-type compounds.

Abstract: Erwinia chrysanthemi 3937 possesses a saturable, high-affinity transport system for the ferric complex of its native siderophore chrysobactin, [N-alpha-(2,3-dihydroxybenzoyl)-D-lysyl-L-serine]. Uptake of 55Fe-labeled chrysobactin was completely inhibited by respiratory poison or low temperature and was significantly reduced in rich medium. The kinetics of chrysobactin-mediated iron transport were determined to have apparent Km and Vmax values of about 30 nM and of 90 pmol/mg.min, respectively. Isomers of chrysobactin and analogs with progressively shorter side chains mediated ferric iron transport as efficiently as the native siderophore, which indicates that the chrysobactin receptor primarily recognizes the catechol-iron center. Free ligand in excess only moderately reduced the accumulation of 55Fe. Chrysobactin may therefore be regarded as a true siderophore for E. chrysanthemi.

The requirement of chrysobactin dependent iron transport for virulence incited by Erwinia chrysanthemi on Saintpaulia ionantha

Abstract: To incite a systemic disease on its specific host, Saintpaulia ionantha, the soft-rot Erwinia chrysanthemi strain 3937 requires a functional high affinity iron transport system. Under iron starvation, strain 3937 produces chrysobactin, a novel catechol-type siderophore. Recent advances in the biochemistry and genetics of iron assimilation in E. chrysanthemi are reported. Analysis of leaf intercellular fluid from healthy and infected plants suggests: (i) leaf vessels in which the bacteria develop during infection would be low in free iron and (ii) chrysobactin could be produced in planta.

Extracellular enzymes and pathogenesis of soft-rot erwinia

Abstract: Historically the genus Erwinia has served as a repository for plant-pathogenic or plant-associated bacteria (25, 96, 128). Consequently, diverse bacteria that occupy different habitats on or within plants and plant remains have been lumped into this genus. Their diversity is also reflected in the range of symp­ toms, i.e. necrosis, wilts, galls, and rots elicited in a wide range of plants. This diversity notwithstanding, these bacteria are related genetically to other en­ terobacteria such as Escherichia coli and Salmonella typhimurium that have served well as model systems for genetic and physiological studies. Microbi­ ologists and plant pathologists alike were initially attracted to Erwinia because of the potential for the use of genetic tools developed for the E. coli system. Thus, several Erwinia species were selected as model systems for the analysis

Potato diseases caused by soft rot erwinias : an overview of pathogenesis

Abstract: Three soft rot erwinias, Erwinia carotovora ssp. carotovora, E. carotovora ssp. atroseptica and E. chrysanthemi are associated with potatoes causing tuber soft rot and blackleg (stem rot). Latent infection of tubers and stems is widespread. As opportunistic pathogens, the bacteria tend to cause disease when potato resistance is impaired. Pathogenesis or disease development in potato tubers and stems is discussed in terms of the interaction between pathogen, host and environment, microbial competition and recent findings on the molecular basis of pathogenicity. Emphasis is placed on the role of free water and anaerobiosis in weakening tuber resistance and in providing nutrient for erwinias to multiply. Blackleg symptoms are expressed when erwinias predominate in rotting mother tubers, invade the stems and multiply in xylem vessels under favourable weather conditions. Soft rot erwinias tend to out-compete other bacteria in tuber rots because of their ability to produce larger quantities of a wider range of cell wall-degrading enzymes. However, despite extensive studies on their induction, regulation and secretion, little is known about the precise role of the different enzymes in pathogenesis. The putative role of quorum-sensing regulation of these enzymes in disease development is evaluated. The role certain pathogenicity-related characters, including motility, adhesion, siderophores, detoxifying systems and the hrp gene complex, common to most bacteria including symbionts and saprophytes, could play in latent and active infections is also discussed.

Regulation of pectinolysis in erwinia chrysanthemi

Abstract: ▪ Abstract Erwinia chrysanthemi is an enterobacterium that causes various plant diseases. Its pathogenicity results from the secretion of pectinolytic enzymes responsible for the disorganization of the plant cell wall. The E. chrysanthemi strain 3937 produces two pectin methylesterases, at least seven pectate lyases, a polygalacturonase, and a pectin lyase. The extracellular degradation of the pectin leads to the formation of oligogalacturonides that are catabolized through an intracellular pathway. The pectinase genes are expressed from independent cistrons, and their transcription is favored by environmental conditions such as presence of pectin and plant extracts, stationary growth phase, low temperature, oxygen or iron limitation, and so on. Moreover, transcription of the pectin lyase gene responds to DNA-damaging agents. The differential expressions of individual pectinase genes presumably reflect their role during plant infection. The regulation of pel genes requires several regulatory systems, incl...

Microbial Iron Acquisition: Marine and Terrestrial Siderophores

Abstract: The vast majority of bacteria require iron for growth.1,2 Iron is an essential element required for key biological processes including amino acid synthesis, oxygen transport, respiration, nitrogen fixation, methanogenesis, the citric acid cycle, photosynthesis and DNA biosynthesis. However, obtaining iron presents challenges for the majority of microorganisms. While iron is the fourth most abundant transition metal in the Earth's crust, the insolubility of iron(III) [Ksp of Fe(OH)3 = 10-39] at physiological pH in aerobic environments severely limits the availability of this essential nutrient. Pathogenic and marine bacteria face similar challenges for obtaining iron because both live in very low iron environments. Bacteria typically require micromolar levels of total iron for growth, yet the iron concentration in the surface waters of the oceans is only 0.01-2 nM.3-7 In humans cellular iron is also very low and is sequestered by lactoferrin, transferrin, and ferritin as a primary defense mechanism at the onset of infection.8 Given its cellular importance, it is not surprising that microbes have evolved multiple pathways designed to extract iron from their surrounding environments, tailored to the molecular constraints of the iron pool (Figure 1). Figure 1 Microbial (Gram negative) iron uptake pathways. In this review the general pathways by which bacteria acquire iron are considered first as an overview to illustrate the singular importance of iron for microbial growth. The focus of this review is on siderophore-mediated iron uptake, particularly structural characteristics of marine siderophores and the reactivity that these characteristics confer. Relatively little is known about marine microbial iron transport compared to that for terrestrial and pathogenic microbes, yet comparison of the structures and reactivity may hint at the biological advantage that these structural traits confer to marine microbes and very possibly provide insights to siderophore-mediated iron uptake in some pathogens.

Siderophores in fungal physiology and virulence.

Abstract: Maintaining the appropriate balance of iron between deficiency and toxicity requires fine-tuned control of systems for iron uptake and storage. Both among fungal species and within a single species, different systems for acquisition, storage, and regulation of iron are present. Here we discuss the most recent findings on the mechanisms involved in maintaining iron homeostasis with a focus on siderophores, low-molecular-mass iron chelators, employed for iron uptake and storage. Recently siderophores have been found to be crucial for pathogenicity of animal, as well as plant-pathogenic fungi and for maintenance of plant-fungal symbioses.