Frank A. Fekete

The isolation and immunolocalization of iron-binding compounds produced by Gloeophyllum trabeum

SummaryLow molecular weight iron-binding compounds are produced by the brown-rot fungus Gloeophyllum trabeum. These chelators may function in scavenging transition metals for fungal metabolism and extracellular enzyme production. Because of the low molecular mass of the chelate-metal complex (below 1000 Da), and the oxidizing potential of the bound transition metals, certain chelating compounds could also play a role in the early stages of cellulose depolymerization by brown-rot fungi. High-affinity iron-binding compounds were isolated and partially purified from both liquid cultures of the brown-rot Gloeophyllum trabeum and from infected wood. Chelating compounds purified by thin-layer chromatography were used to prepare specific antibodies. These antibodies were shown to detect the chelator in infected wood and liquid fungal cultures by enzyme-linked immunosorbent assay and could be used in immunotransmission electron microscopy to visualize the high-affinity iron-binding compounds in situ. Elucidating the physiological roles of fungal chelate-metal complexes and determining their function in lignocellulose depolymerization will help us to better understand the mechanism of wood biodegradation.

Co-selection of mercury and antibiotic resistance in sphagnum core samples dating back 2000 years.

Metal exposure might induce multiple drug resistance (MDR) in bacteria in environments devoid of antibiotics via the process of co-selection, but the extent is poorly known. Core samples from two sphagnum peat bogs in central Maine, USA, were analyzed for total Hg content and were radiocarbon dated. Culturable bacteria isolated from various core depths were assayed for antibiotic- and Hg-resistance and the presence of merA (mercuric reductase). Our results show that sphagnum peat bogs represent natural ecosystems that contain ambient levels of Hg that select for indigenous bacterial strains that are not only Hg resistant, but also possess the MDR phenotype.

Identification of a multidrug efflux pump in Flavobacterium johnsoniae

In this study, the mechanism conferring multiple drug resistance in several strains of flavobacteria isolated from the ovarian fluids of hatchery reared 3-year old brook trout Salvelinus fontinalis was investigated. Metabolic fingerprinting and 16S rRNA gene sequences identified the isolates as Flavobacterium johnsoniae. The isolates exhibited multiple resistances to a wide range of antimicrobial classes including penicillin, cephem, monobactam, aminoglycoside, and phenicol. Although plasmids and other transposable elements containing antimicrobial resistance genes were not detected, the isolates did contain a genomic sequence for a chloramphenicol-inducible resistance-nodulation-division family multidrug efflux pump system. Efflux pumps are non-specific multidrug efflux systems. They are also a component of cell-cell communication systems, and respond specifically to cell membrane stressors such as oxidative or nitrosative stress. Understanding of efflux pump mediated antibiotic resistances will affect efficacy of clinical treatments of fishes associated with F. johnsoniae epizootics.

Capsular extracellular polysaccharide and hydroxamate formation by iron‐deficient azotobacter chroococcum B‐8

Abstract The free‐living diazotroph Azotobacter chroococcum B‐8 requires a high complement of Fe to support nitrogen fixation. The yield of capsular extracellular polysaccharide (EPS) and the formation of high‐affinity Fe‐binding compounds were used to measure the response of A. chroococcum B‐8 to iron‐stressed growth conditions. Cultures were nutritionally stressed for Fe by successive transfers on Fe‐deficient nitrogen‐free solid‐plating media, or on the same media supplemented with NO3‐ or NH4 + as the sources of fixed nitrogen. Under all nitrogen growth conditions, the same two anodally‐migrating Fe‐binding compounds were detected using the paper electrophoresis siderophore assay. Both Fe‐binding compounds were Csaky positive for bound hydroxylamines and both relieved the growth requirement of the hydroxamate auxotroph, Arthrobacter flavescens JG‐9. Fe‐deficient liquid cultures, grown in the presence of N2, NO3 ‐, or NH4 +, produced much higher levels of hydroxamate over the Fe‐sufficient control cult...