Genetic Structure of Acetobacter diazotrophicus Populations and Identification of a New Genetically Distant Group

Abstract

A total of 55 isolates of Acetobacter diazotrophicus recovered from diverse sucrose-rich host plants and from mealybugs associated with sugarcane plants were characterized by the electrophoretic mobilities of 12 metabolic enzymes. We identified seven different electrophoretic types (ETs), six of which are closely related within a genetic distance of 0.195 and exhibit high DNA-DNA homology. The seventh ET was largely divergent, separated at a genetic distance of 0.53, and had only 54% DNA homology to the reference strain. Strains corresponding to ET 7 could represent a distinct nitrogen-fixing species of the genus Acetobacter. More genetic diversity was found in isolates from Brazil than in those from Mexico, probably due to the very different crop nitrogen fertilization levels used.

Microbial fructosyltransferases and the role of fructans

“…It is not known under which conditions lsdB is transcribed, or if it can be transcribed at all. lsdA shows restriction fragment length polymorphisms among strains isolated from Australia, Brazil, Cuba or México, which show low genetic variability by multilocus enzyme electrophoresis typing (Caballero-Mellado et al 1995). Near the 3¢ end of lsdB, there is a cluster of genes that encode components of a type II secretion system, probably constituting an operon ).…”

A N2-fixing endophyticBurkholderiasp. associated with maize plants cultivated in Mexico

“…For each sample, aliquots of the highestdilution tubes were streaked onto modified PCAT agar plates. For each plate, three colonies were characterized by multilocus enzyme electrophoresis (MLEE) profiles, following the procedures described by Caballero-Mellado et al (1995), to verify that these colonies corresponded to the inoculated isolates.…”

Colonization of sugarcane by Acetobacter diazotrophicus is inhibited by high N-fertilization

“…It has been reported that the frequency of isolation of A. diazotrophicus from sugarcane plants diminishes in relation to the amounts of N‐fertilization used in the fields [10, 11]. Caballero‐Mellado et al [12] found that Brazilian isolates were genetically more diverse than Mexican ones and suggested that this could be related to the difference in nitrogen fertilization levels between the two countries, in such a manner that the application of more fertilizer caused a diminished diversity. In the nitrogen‐fixing symbiosis of Rhizobium and legumes, high nitrogen fertilization abolishes nodulation or, when applied to existing nodules, nitrogen fixation.…”