Integration Host Factor Is Essential for Biofilm Formation, Extracellular Enzyme, Zeamine Production, and Virulence in Dickeya zeae

Abstract

Dickeya zeae is a globally important pathogenic bacterium that infects a number of crops, including rice, maize, potato, and banana. Bacterial foot rot of rice caused by D. zeae is one of the most important bacterial diseases of rice in China and some Southeast Asian countries. To investigate the functions of integration host factor (IHF) in D. zeae, we generated knockout mutants of ihfA and ihfB. Phenotypic assays showed that both the ΔihfA and ΔihfB strains had greatly reduced mobility, biofilm formation, extracellular protease and pectinase activities, and toxin production compared with the wild-type strain. In addition, the mutants did not inhibit the germination of rice seeds, failed to cause soft rot in potatoes and a hypersensitive response in tobacco, and were avirulent in rice. Quantitative reverse-transcription polymerase chain reaction analysis demonstrated that IHF positively regulates the expression of zmsA, hrpN/Y, pelA/B/C, pehX, celZ, prtG, fliC, and DGC. Electrophoretic mobility shift assays further confirmed that IhfA binds to the promoter region of the diguanylate cyclase gene and alters the levels of a second bacterial messenger, c-di-GMP, to regulate the pathogenicity or other physiological functions of D. zeae. In summary, IHF is an important integrated regulator of pathogenicity in D. zeae.

The nucleoid-associated protein IHF acts as a “domainin” protein coordinating the bacterial virulence traits with global transcription

“…The phenotypic traits affected by ihfA mutation in D. dadantii are by large similar to those reported in a recent study of Dickeya zeae strain lacking IHF [34]. However, there are also interesting differences.…”

“…In various Salmonella species IHF is shown to profoundly influence the expression of virulence genes, facilitate invasion associated with transition of bacterial cells to stationary phase [29] and promote biofilm formation [30]. IHF positively regulates the expression of virulence traits in human pathogens Vibrio cholerae [31] and Vibrio fluvialis [32] as well as in plant pathogens Erwinia amylovora [33] and Dickeya zeae [34]. In the soil bacterium Pseudomonas putida, IHF activates the genes involved in adaptation to the post-exponential phase with limited effect on genes involved in central metabolism [35].…”

Integration host factor regulates colonization factors in the bee gut symbiontFrischella perrara

“…Alternatively, IHF may act upstream of another regulator that controls the expression of the identified genes. In the plant pathogen Dickeya zeae , IHF was suggested to positively regulate different virulence factors through binding to the promoter region of a diguanylate cyclase gene, increasing the production of the secondary messenger c-di-GMP (65). In F. perrara , we found that the transcriptional regulators BasR and DksA were substantially downregulated in the wt versus the ihfA* mutant.…”

Participation 0f Banana Intolerance in AtherosclerosisReview 0f the Literature

“…Banana starch along with these lactobacilli decreases pH, increases the production of lactic acid and short chain fatty acids from the intestinal microbiota (: a source of energy for the intestinal cells) and inhibits the population of others e.g. salmonella typhimurium SA2093 [90]. The plant fibers include polysaccharides, oligosaccharides and inulin which are fermented with intestinal microbiota influencing its composition and activity [91].…”