Potential PGPR properties of cellulolytic, nitrogen-fixing, and phosphate-solubilizing bacteria of a rehabilitated tropical forest soil

Abstract

21In the midst of major soil degradation and erosion faced by tropical ecosystems, 22 rehabilitated forests are established to avoid further deterioration of forest land. In this context, 23 cellulolytic, nitrogen-fixing (N-fixing), and phosphate-solubilizing bacteria are very important 24 functional groups in regulating the elemental cycle and plant nutrition, hence replenishing the 25 nutrient content in forest soil. As other potential plant growth-promoting (PGP) rhizobacteria, 26 these functional bacteria could have cross-functional abilities or beneficial traits that are 27 essential for plants and improve their growths. This study was conducted to isolate, identify, and 28 characterize selected PGP properties of these 3 functional groups of bacteria from tropical 29 rehabilitated forest soils at Universiti Putra Malaysia Bintulu Sarawak Campus, Malaysia. 30 Isolated cellulolytic, N-fixing and phosphate-solubilizing bacteria were characterized for 31 respective functional activities, biochemical properties, molecularly identified, and assessed for 32 PGP assays based on seed germination and indole-3-acetic acid (IAA) production. Out of 15 33 identified bacterial isolates exhibiting beneficial phenotypic traits, a third belong to genus 34 Burkholderia and a fifth to Stenotrophomonas sp. with both genera consisting of members from 35 two different functional groups. Among the tested bacterial strains, isolate Serratia 36 nematodiphila C46d, Burkholderia nodosa NB1, and Burkholderia cepacia PC8 showed 37 outstanding cellulase, N-fixing, and phosphate-solubilizing activities, respectively. The results 38 of the experiments confirmed the multiple PGP traits of selected bacterial isolates based on 39 respective high functional activities, root, shoot lengths, and seedling vigour improvements 40 when bacterized on mung bean seeds, as well as presented some significant IAA productions. 41The results of this study indicated that these functional bacterial strains could potentially be 42 included in future biotechnological screenings to produce beneficial synergistic effects via their 43 versatile properties on improving soil fertility and possible crop growth stimulation. 44 Keywords: rehabilitated tropical forest soil; cellulolytic bacteria; N-fixing bacteria; phosphate-45 solubilizing bacteria; PGP traits 3 46 Introduction 47 Albeit vast in carbon and biodiversity, tropical ecosystems are facing major 48 deforestations, leading to widespread soil erosion which garnered much recent attention 49 [1-3]. As soil erosion aggravates, the soil loss overrides soil establishment, which 50 results in diminishing soil resources and the ecosystem supports they render [4-5], in 51 particularly manifested as low productivity and farming sustainability on the degraded 52 soils [6]. Planted forest or rehabilitation efforts are undertaken to avoid further 53 deterioration of forest land. 54 Bacteria has large biodiversity composition in soils, and thus, is major 55 participant of soil principal processes that regulate whole terrest...

Phosphate Solubilizing Rhizobacteria Could Have a Stronger Influence on Wheat Root Traits and Aboveground Physiology Than Rhizosphere P Solubilization

“…Multiple beneficial effects of soil microorganisms have widely been identified as key drivers for a better plant growth and increased soil P availability (Kumar, 2016;Peŕez et al, 2016;Bargaz et al, 2018). PGPR exhibiting high PSC have been described to benefit plant growth and yield when associated with roots and even within other plant parts such as leaves (Fahad et al, 2015;Jambhulkar et al, 2016;Tang et al, 2018). For example, application of efficient phosphate solubilizing bacteria (PSB) such as Bacillus megaterium increased soil P availability by nearly 30% (Alzoubi and Gaibore, 2012).…”

Seed biopriming using saline soil rhizobacteria from the coast of Kolaka Regency for enhancing seed viability and vigor of tomato (Lycopersicum esculentum L.)

“…Rhizobacteria that thrive in saline soil have the ability to stimulate increased plant development via a number of different mechanism, one of which is the bacteria's capacity to produce growth hormones like as gibberellins, cytokinin, and AIA [13]. Several other research results have also proven that rhizobacteria isolated from saline soil are not only capable of producing growth hormones, but also biological nitrogen fixation, dissolving phosphate and potassium [14]. In addition to the ability to produce various growth-promoting attributes previously described, plants inoculated with saline soil rhizobacteria were also able to improve a number of physiological functions such as reducing osmotic stress, increasing K+ uptake and decreasing Na+ uptake [15].…”

Indigenous Peat Cellulolytic Bacteria and Its Potential as A Liberica Coffee Growth Promoter

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