Parasitic growth of Pseudomonas aeruginosa in co‐culture with the chitinolytic bacterium Aeromonas hydrophila

Abstract

SummaryPolymer-degrading bacteria face exploitation by opportunistic bacteria that grow with the degradation products without investing energy into production of extracellular hydrolytic enzymes. This scenario was investigated with a co-culture of Aeromonas hydrophila and Pseudomonas aeruginosa with chitin as carbon, nitrogen and energy source. In single cultures, A. hydrophila could grow with chitin, while P. aeruginosa could not. Co-cultures with both strains had a biphasic course. In the first phase, P. aeruginosa grew along with A. hydrophila without affecting it. The second phase was initiated by a rapid inactivation of and a massive acetate release by A. hydrophila. Both processes coincided and were dependent on quorum sensing-regulated production of secondary metabolites by P. aeruginosa. Among these the redox-active phenazine compound pyocyanin caused the release of acetate by A. hydrophila by blocking the citric acid cycle through inhibition of aconitase. Thus, A. hydrophila was forced into an incomplete oxidation of chitin with acetate as end-product, which supported substantial growth of P. aeruginosa in the second phase of the co-culture. In conclusion, P. aeruginosa could profit from a substrate that was originally not bioavailable to it by influencing the metabolism and viability of A. hydrophila in a parasitic way.

Flexible Survival Strategies of Pseudomonas aeruginosa in Biofilms Result in Increased Fitness Compared with Candida albicans

“…aeruginosa previously has been shown to efficiently block growth of other microorganisms. It was shown, for example, that supernatants of P. aeruginosa co-cultured with Aeromonas hydrophila contained rhamnolipids and the siderophores pyoverdine and pyocyanin, which caused inactivation of A. hydrophila (89). A combination of pyocyanin and 1-hydroxyphenazine was shown to inhibit yeast mycelia transformation and growth of C. albicans and Aspergillus fumigatus (36).…”

Interkingdom Cross-Feeding of Ammonium from Marine Methylamine-Degrading Bacteria to the Diatom Phaeodactylum tricornutum

“…Growth experiments with bacterial strains in monocultures were performed in 10-ml test tubes containing 3 ml SW-f/2 medium that were incubated at 30°C on a rotatory shaker at 200 rpm (Orbital Shaker 3015; GFL, Germany). Growth was measured by optical density at a wavelength of 600 nm (OD 600 ) in a photometer (spectrophotometer M107; Camspec, United Kingdom) or by CFU as described previously (30) by decimally diluting cultures in SW-f/2 medium without carbon and nitrogen sources and plating appropriate dilution steps on SW-f/2 plates containing 10 mM glucose and 2 mM MMA. Precultures of both strains were inoculated from solid medium; main cultures were inoculated from precultures to an OD 600 of 0.01.…”

Uncoupling of chitinase activity and uptake of hydrolysis products in freshwater bacterioplankton

“…Also, commensal populations that do not express chitinases but incorporate released hydrolysis products would be favored by such excess polymer hydrolysis. Accordingly, there are early observations that some isolates obtained from chitin-containing particles can grow on NAG but not on polymeric chitin, and it was suggested that those organisms benefit from NAG produced by their chitinase-producing neighbors (Kaneko and Colwell 1978). It has furthermore been shown that a non-chitinolytic Escherichia coli strain can grow on diNAG as its sole carbon source (Keyhani and Roseman 1997) and more recent experiments on bacterial laboratory strains point to the existence of commensal or even parasitic relationships between chitin degraders and chitin users (Everuss et al 2008;Jagmann et al 2010).…”