Indole-3-Acetic Acid Biosynthesis Is Deficient in Gluconacetobacter diazotrophicus Strains with Mutations in Cytochrome c Biogenesis Genes

Abstract

Gluconacetobacter diazotrophicus is an endophyte of sugarcane frequently found in plants grown in agricultural areas where nitrogen fertilizer input is low. Recent results from this laboratory, using mutant strains of G. diazotrophicus unable to fix nitrogen, suggested that there are two beneficial effects of G. diazotrophicus on sugarcane growth: one dependent and one not dependent on nitrogen fixation. A plant growth-promoting substance, such as indole-3-acetic acid (IAA), known to be produced by G. diazotrophicus, could be a nitrogen fixation-independent factor. One strain, MAd10, isolated by screening a library of Tn5 mutants, released only ϳ6% of the amount of IAA excreted by the parent strain in liquid culture. The mutation causing the IAA ؊ phenotype was not linked to Tn5. A pLAFR3 cosmid clone that complemented the IAA deficiency was isolated. Sequence analysis of a complementing subclone indicated the presence of genes involved in cytochrome c biogenesis (ccm, for cytochrome c maturation). The G. diazotrophicus ccm operon was sequenced; the individual ccm gene products were 37 to 52% identical to ccm gene products of Escherichia coli and equivalent cyc genes of Bradyrhizobium japonicum. Although several ccm mutant phenotypes have been described in the literature, there are no reports of ccm gene products being involved in IAA production. Spectral analysis, heme-associated peroxidase activities, and respiratory activities of the cell membranes revealed that the ccm genes of G. diazotrophicus are involved in cytochrome c biogenesis.

Isolation and characterization of culturable endophytic actinobacteria associated with Artemisia annua L.

“…These organisms seem to have important roles in plant development and health because they can promote plant growth by nutrient assimilation or phytohormone production. In addition they can act as antagonists against phytopathogens through the production of antibiotics or siderophores, nutrient competition and induction of systemic disease resistance (Kunoh 2002;Lee et al 2004;Bailey et al 2006;Hasegawa et al 2006;Meguro A 2006;Conn 2008;Qin et al 2011). It has also reported that several actinobacteria discovered from plants produce different kinds of secondary metabolites, which might be promising sources of novel antibiotics and growth regulators of other organisms (Castillo et al 2006;Hasegawa et al 2006;Qin et al 2011).…”

The use of Sprout as Precursor for the Production of Indole Acetic Acid by Selected Plant Growth Promoting Rhizobacteria Grown in the Fermentor

“…It was possible that conversion of the mung bean sprout extract and fish extract to tryptophan was much lower than 200 ppm and consequently the production IAA were about 25 ppm. According to Lee et al (2004), in presence of higher concentration of tryptophan, the microbes release greater quantities of IAA and related compounds. The using of tryptophan in this work was as positive control.…”

Bacterial Community Associated with Autotrophic and Heterotrophic Cultures of Medicinal Plant Smallanthus sonchifolius (Yacon)

“…Our data suggest that the isolates recovered from in vitro yacon cultures were endophytes except for F. oryzihabitans, which grew endo and epiphytically. Several reports indicate that plant growth promoting bacteria are beneficial endophytes growing in association with the host [21][22][23]. Among the S. sonchifolius isolates, Microbacterium imperiali and Sphingomonas paucimobilis were the highest IAA producers ( Table 4).…”