Endophytic bacteria live alongside rhizobia in the nodules of legumes and can boost soil fertility by enhancing stress tolerance, producing growth-promoting hormones, and improving nutrient absorption.

The aim of this study was to isolate and characterize endophytic bacterial strains from the nodules of Lathyrus. A total of 301 strains were collected through direct sampling or trapping from soil samples gathered from different regions in Algeria. Twelve potential plant growth-promoting strains were then selected for their high inorganic phosphate-solubilizing ability. These strains were screened for enzymatic activities, including cellulase, protease, esterase, and urease production, which are critical for nutrient mobilization and plant growth promotion. API NE strips were used to obtain a comprehensive biochemical profile of the isolated endophytes.

The results demonstrated that oxidase exhibited the highest level of positive isolates, followed by DNase. Significant enzymatic activities were observed for pectinase and lipase, while moderate levels were detected for esterase and cellulase activities. Urease showed low levels of positive isolates, and none of the isolates tested positive for gelatinase. These findings underscore the metabolic diversity and potential agricultural benefits of the endophytic isolates in enhancing soil fertility, nutrient cycling, and plant health. The API 20 NE results revealed that glucose and arabinose assimilation, along with esculin hydrolysis, had the highest levels of positive isolates. β-galactosidase was also notable. Moderate activity levels were observed for arginine dihydrolase, while lower levels of positive isolates were seen for nitrate reduction, tryptophan deamination, and gelatin hydrolysis.

The promising enzymatic activities and plant growth-promoting traits of these endophytes make them suitable candidates for the development of eco-friendly agricultural inputs aimed at enhancing crop productivity and sustainability.