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).
Escherichia coli USML2 endofitik yang asalnya dipencilkan daripada bahagian dalaman tisu daun kelapa sawit (Elaeis guineensis Jacq.) telah diinokulat kepada anak benih padi untuk menilai kemampuan E. coli USML2 untuk kolonisasi tisu dalaman dan menggalakkan pertumbuhan perumah. Jangkitan E. coli USML2 bermula dengan kolonisasi bakteria pada permukaan akar, pencerobohan tisu dalaman akar dan diikuti oleh penyebaran endofitik. Inokulasi E. coli USML2 di zon rhizosfera padi mengakibatkan peningkatan jumlah daun yang ketara (33.3%), kandungan klorofil (33.3%), tinggi tunas (34.8%) dan berat kering (90.4%) anak benih padi berusia 42 hari berbanding kawalan. Penemuan ini juga menunjukkan kemampuan E. coli USML2 untuk tersebar secara endofitik yang berfungsi sebagai strategi bermanfaat bakteria untuk kolonisasi tanaman dan mendapat perlindungan terhadap keadaan tanah yang tidak sesuai. Maklumat genom E. coli USML2 juga telah mengungkapkan ramalan gen yang penting untuk kolonisasi bakteria endofitik dan penggalak pertumbuhan perumah dan mengukuhkan potensi E. coli USML2 sebagai Endofit Penggalak Pertumbuhan Tanaman (PGPE).
Keywords: Endophytic Colonisation; Escherichia coli USML2, PGPE; Plant Growth Promotion.
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