Abstract
Immense quantities of chitin are catabolized by marine bacteria, and this process involves at least three signal transduction systems in Vibrio furnissii. One system, chemotaxis to chitin oligosaccharides, is probably used to colonize chitin particles. But how do the first few cells find this highly insoluble polysaccharide? The following hypothesis is proposed to answer this question: the bacteria respond to soluble chemo-attractants in exudates from injured organisms. Virtually all chitin-producing organisms also contain glucose and/or trehalose, often at high concentrations such as trehalose in insect hemolymph. Chemotaxis of V. furnissii was therefore studied with a variety of sugars. Fructose, ribose, and glycerol are catabolites but not attractants. The cells exhibit weak constitutive taxis to Glc and GlcNAc. After induction, they show a weak response to galactose but are strongly attracted to the following substrates of the phosphoenolpyruvate:glycose phosphotransferase system (PTS): GlcNAc, trehalose, glucose, sucrose, mannose, and mannitol. There is a rough qualitative but no quantitative correlation between the rate of phosphorylation and the chemotactic response to PTS sugars. Trehalose is especially noteworthy because it is phosphorylated at a very rapid rate by uninduced cells but is not an attractant until the cells are induced. We suggest that unidentified inducible factors link the PTS to chemotaxis.
Highlights
Immense quantities of chitin arecatabolized by ma- non
The process requires more than two rine bacteria, and this process involves at least three dozeninducible proteinsand a minimum of three signal signal transduction systemsin Vibrio furnissii
The cells exhibit weak constitutive taxis to Glc and GlcNAc. They show a weak response to galactose but are strongly attracted to the following substrates of the phosphoeno1pyruvate:glycose phosphotransferase system (PTS): GlcNAc, trehalose, glucose, sucrose, [7]. Part of this apparatus isa (GlcNAc),binding lectin. ( b ) Chemotaxis receptors that arespecific for chitin oligosaccharides
Summary
(Received for publication, October 13, 1992,and in revised form, January 5, 1993). From the McCollum-Pratt Institute andthe Department of Biology, The Johns Hopkins Uniuersity, Baltimore, Maryland 21218. We suggest that unidentified inducible factors linkthe PTS to chemotaxis Artificial sea water mediumand induced with 0.6mM of the indicated compound, conditionsthat are optimal for inducingtaxis to GlcNAc and the chitin oligosaccharides [8].The cellswere harvested and washedwith Taxis buffer (50% artificial seawater, 0.1% NHaCl, 0.002%K2HP04,50 mM HEPES buffer, pH7.5) at room temperature. The mixtures were incubated at 30"Cfor min, reactions ter- induced with fructose exhibited taxis to Glc and to GlcNAc, minated by heating at 100 "Cfor 5 min, and the quantity of labeled sugar-phosphate determined by anion-exchangechromatography [16]. The results were the same as those obtained with the labeled sugar,both with uninduced and induced cell suspensions.There was no detectable Glc-6-P in the eluate from the ion-exchange column support growthof V. furnksii are listed in TablIe11 of Ref. 7 and in TableI of this report.
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