Abstract
An endophytic Escherichia coli USML2 originally isolated from the inner part of an oil palm (Elaeis guineensis Jacq.) leaf tissue was inoculated to rice seedlings to investigate its ability in colonising plant inner tissues and promoting growth. Infection of E. coli USML2 was initiated by colonisation on the root surface, invasion of the interior root system followed by endophytic spreading. Inoculation of E. coli USML2 in the rice rhizosphere zone resulted in a significant increase in leaf numbers (33.3%), chlorophyll content (33.3%), shoot height (34.8%) and plant dry weight (90.4%) of 42 days old rice seedlings as compared to the control. These findings also demonstrated the ability of E. coli USML2 to spread endophytically which serves as a beneficial strategy for the bacterium to colonise the host plant and gain protection against adverse soil conditions. The genome of E. coli USML2 had also revealed predicted genes essential for endophytic bacterial colonisation and plant growth promotion which further proven potentials of E. coli USML2 as Plant Growth Promoting Endophyte (PGPE).
Highlights
Escherichia coli is a harmless natural inhabitant of the gastrointestinal tract of animals and humans (Ingerson-Mahar & Reid 2011)
An endophytic Escherichia coli USML2 originally isolated from the inner part of an oil palm (Elaeis guineensis Jacq.) leaf tissue was inoculated to rice seedlings to investigate its ability in colonising plant inner tissues and promoting growth
E. coli USML2 was able to colonise the rhizoplane and internal tissues of root, stem and leaf of the host plants grown under aseptic conditions (Table 1)
Summary
Escherichia coli is a harmless natural inhabitant of the gastrointestinal tract of animals and humans (Ingerson-Mahar & Reid 2011). Substantial nutrient supplies in soil are provided from excretion of root exudates that consist of carbohydrates, amino acids, organic acids, vitamins and phytohormones acting as chemoattractants to which bacteria respond (Narula et al 2009; Pedraza et al 2009; Nautiyal et al 2010; Berg et al 2013) This condition attracts broad diversities of soil bacteria to live in the rhizosphere zone and E. coli strains must compete for survival (Berg et al 2013; Dudeja & Giri 2014). This is probably the reason why E. coli has been frequently found endophytically in interior plant tissues of plants where the surrounding environment is free from faecal contamination (Dublan et al 2014). Hardoim et al (2008) claimed that E. coli with the ability to live and persist in planta are known as endophytes
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