Effect of oxygen on the growth and biofilm formation of Xylella fastidiosa in liquid media.

Xylella fastidiosa is a xylem-limited bacterial pathogen, and is the causative agent of Pierce's disease of grapevines and scorch diseases of many other plant species. The disease symptoms are putatively due to blocking of the transpiration stream by bacterial-induced biofilm formation and/or by the formation of plant-generated tylosis. Xylella fastidiosa has been classified as an obligate aerobe, which appears unusual given that dissolved O2 levels in the xylem during the growing season are often hypoxic (20-60 μmol L(-1)).

Nitrification and denitrification gene abundances in swine wastewater anaerobic lagoons.

Although anaerobic lagoons are used globally for livestock waste treatment, their detailed microbial cycling ofN is only beginning to become understood. Within this cycling, nitrification can be performed by organisms that produce the enzyme ammonia monooxygenase. For denitrification, the reduction of nitrite to nitric oxide can be catalyzed by two forms of nitrite reductases, and N,O can be reduced by nitrous oxide reductase encoded by the gene nosZ The objectives of this investigation were to (i) quantify the abundance of the amoA, nirK, nirS, and nosZ genes; (ii) evaluate the influence of environmental conditions on their abundances; and (iii) evaluate their abundance relative to denitrification enzyme activity (DEA).

Characterization of a microbial community capable of nitrification at cold temperature.

While the oxidation of ammonia is an integral component of advanced aerobic livestock wastewater treatment, the rate of nitrification by ammonia-oxidizing bacteria is drastically reduced at colder temperatures. In this study we report an acclimated lagoon nitrifying sludge that is capable of high rates of nitrification at temperatures from 5 degrees C (11.2mg N/g MLVSS/h) to 20 degrees C (40.

Influence of xylem fluid chemistry on planktonic growth, biofilm formation and aggregation of Xylella fastidiosa.

Xylella fastidiosa is the causal agent of Pierce's disease in grapevines. The mechanisms of pathogenicity are largely due to occlusion of xylem vessels by aggregation of X. fastidiosa and biofilm formation.