Iron in Neisseria meningitidis: minimum requirements, effects of limitation, and characteristics of uptake

Abstract

A simple defined medium (neisseria defined medium) was devised that does not require iron extraction to produce iron-limited growth of Neisseria meningitidis (SDIC). Comparison of this medium to Mueller-Hinton broth and agar showed nearly identical growth rates and yields. The defined medium was used in batch cultures to determine the disappearance of iron from the medium and its uptake by cells. To avoid a number of problems inherent in batch culture, continuous culture, in which iron and dissolved oxygen were varied independently, was used. Most of the cellular iron was found to be nonheme and associated with the particulate fraction in sonically disrupted cells. Nonheme and catalase-heme iron were reduced by iron starvation far more than cytochromes b and c and

Meningococcal biofilm formation: structure, development and phenotypes in a standardized continuous flow system

“…In this study we established a biofilm model, in which N. meningitidis was grown under flow conditions in a chemically defined biofilm medium to guarantee stable nutritional conditions and high reproducibility. We used a modification of the defined growth medium NDM (Archibald and DeVoe, 1978). NDM was modified by addition of PolyViteX and 5 mM NaHCO 3 to yield more reproducible biofilms under flow conditions than with the original NDM.…”

Energy-independent uptake of iron from citrate by isolated outer membranes of Neisseria meningitidis

“…The procedures for routine maintenance of stock cultures and checks for strain purity have been described elsewhere (10). The formulation for the Neisseria defined medium (NDM) used was described previously (2). Cells from frozen (-70°C) working slant cultures on Mueller-Hinton agar (Difco Laboratories, Detroit, Mich.) were cultured as a lawn on NDM agar containing added iron (final concentration, 50 ng of ferrous ammonium sulfate per ml) for 13 h (370C, 5% CO2 in air, high humidity).…”

“…When membranes from whole cells were loaded with iron, stationary-phase cells in their iron-depleted growth medium were treated with 2 mM KCN for 15 min before the addition of 'Fe-(di)citrate complexes at the concentrations and specific activities described above. This procedure permits energy-independent saturation of the iron uptake system, while at the same time preventing the energy-dependent uptake (incorporation) of iron by meningococci (2). Cells were harvested after 5 min in the solution containing 'Fe-dicitrate complexes by centrifugation at 10,000 x g for 10 min; these cells washed twice by resuspension in and centrifugation from a solution containing 0.05 M MOPS (pH 7.5), 360 ,uM sodium citrate, and 2 mM KCN.…”

“…The acquisition of iron from vertebrate hosts has been associated with the ability of a variety of pathogenic microbes to establish and maintain infections (35). Iron is an essential nutrient for nearly all bacteria (26,27), including meningococci (2). Therefore, the mechanism of iron acquisition from hosts is an important consideration among the factors involved in meningococcal pathogenicity.…”

Hydroxamate siderophore secretion by Pseudoalteromonas haloplanktis during steady-state and transient growth under iron limitation

“…haloplanktis exhibited the typical physiological response to Fe-deficient conditions by upregulating siderophore production. Other studies have also documented overproduction of siderophores by bacteria in late growth phase cultures (McIntosh & Earhart 1977, Heinrichs et al 1999, Temirov et al 2003 and have shown that it coincided with a significant decrease in bacterial Fe quota (McIntosh & Earhart 1977, Archibald & Devoe 1978. The observation that ETS activity remained constant while hydroxamate concentration increased suggests that large changes in Fe quota were not likely occurring during onset of siderophore secretion in P. haloplanktis.…”