Plant growth promoting potentials of novel phosphate-solubilizing bacteria isolated from rumen content of White Fulani cattle, indigenous to Nigeria

Phosphate-solubilizing bacteria (PSB) with plant growth promoting (PGP) traits enhance sustainable agriculture. Due to this, bacteria capable of promoting the growth of plants were isolated from rumen content of indigenous White Fulani cattle. The phosphate solubilizing potentials of the bacterial isolates and their plant growth promoting activities were assessed following standard techniques. The total bacterial population in the rumen contents ranged from 5.20 +/- 0.36 x 10(5) to 4.00 +/- 0.01 x 10(6) CFU g(- 1)). Out of 23 isolates, 61% exhibited varying P-solubilization efficiency which ranged between 144 mu g mL(- 1) and 687.75 mu g mL(- 1). Other plant growth promoting activities differed among bacterial isolates. The 16 S rRNA gene sequencing analysis confirmed 57% of the isolates that expressed multiple PGP ability as either Pseudomonas aeruginosa or Escherichia coli. Among the genus Escherichia, E. coli AKRC16 showed most promising result by liberating 345 mu g mL(- 1) soluble P. Overall, P. aeruginosa AKRC7 showed highest PGP activity (687.75 mu g P mL(- 1)) at pH 4.2 after 120 h, IAA (39.27 mu g mL(- 1)), ammonia (3.89 mu mol mL(- 1)) and also displayed ability to fix nitrogen. P. aeruginosa AKRC7, E. coli AKRC16 and E. coli AKRC4 consistently, in that order, exhibited highest productivity for both enzymes at the same pH (6), incubation time (24 h), and optimal source of nitrogen and carbon for phosphatase (tryptone and starch) and phytase (peptone and glucose) correspondingly. Furthermore, P. aeruginosa AKRC7 and E. coli AKRC16 enhanced 100% germination of tomato seeds with significantly high vigour index (2177 and 2114.33) and P content (309.04 +/- 0.05 mg g(- 1) and 301.01 +/- 0.02 mg g(- 1)) of seedlings respectively. The findings revealed rumen content as potential reservoir of prominent PGPB and presented P. aeruginosa AKRC7 (MK332569) and novel strains of E. coli AKRC4 (MK332563) and AKRC16 (MK332576) as promising candidate for bio-inoculation.