The use of lacZ marker in enumeration of Azotobacter chroococcum in carrier based inoculants

Abstract

A transconjugant of Azotobacter chroococcum Mac 27 tagged with lac Z(A. chroococcum Mac27 L) was found to possess high levels of β-galactosidase activity constitutively. Further, the lac Z marker was found to be stably integrated into the chromosome of the A. chroococcum Mac 27 and did not have any adverse effect on growth, nitrogen fixation and excretion of ammonia. A quick method to determine the viable cell number in broth culture and carrier based inoculants has been developed on the basis of β-galactosidase assay. It was found that there was a direct relationship between the number of cell as determined by standard plate count and intensity of colour that developed upon degradation of ONPG due to β-galactosidase activity. The method was found to be sensitive enough to determine 1.7 × 106 CFU mL−1 in broth culture as well as carrier based Azotobacter inoculants. Further, it was observed that when A. chroococcum Mac27 L was inoculated on Brassica campestris, it could be detected in the presence of other bacteria capable of growing on Burks agar medium containing X-gal on the basis of lac Z genetic marker.

Isolation and Characterization of Pseudomonas chlororaphis Strain ST9; Rhizomicrobiota and in Planta Studies

“…For example, in Chaudhary et al (2013) [ 57 ] Azotobacter strain ST24 colonized well the wheat rhizosphere decreasing during growth and reaching a density of 10 4 cfu/mL at 90 days after sowing. Similarly, Solanki and Garg (2014) [ 58 ] reported that Azotobacter on Brassica campestris persisted at 30 and 60 day post-inoculation being approximately 2 × 10 4 cfu per plant at 60 dpi. Mosquito et al (2020) [ 59 ] demonstrated that a Kosakonia sp.…”

Ecological Monitoring of Lacz Marked Strain of Azotobacter Chroococcum in the Rhizoplane of Triticum Aestivum

“…They also reported that upper root parts were effectively colonized upon seed inoculation of Maize with MPB1, while soil inoculation resulted in a complete colonization of the root system. Krishnan and Pueppke 9 also reported that gene fusions can be used to greatly simplify the assessment of nodulation competitiveness in rhizobia, Kamboj et al 10 13 have found lac Z marker to be reliable in detection of inoculated strains in soil as well as in charcoal based inoculants.…”