Influence of Paraquat on Four Rhizobacteria Strains: Pantoea agglomerans, Rhizobium nepotum, Rhizobium radiobacter and Rhizobium tibeticum

Abstract

Background: Soil microorganisms are exposed to herbicides after treatment, which leads to their interaction. The result of this interaction may be the degradation of the herbicides by the microorganisms and by the way, they use the degradation products as an energy source for their own physiological processes, or herbicides have a toxic effect on these microorganisms. Herbicide toxicity becomes severe instantly after application when its concentration in soil is the highest. Paraquat is one of the most widely used herbicides in agriculture; inappropriate use of this herbicide represents an immense pollution problem for soil, therefore on microorganisms. However, the knowledge about the effect of paraquat on soil microorganisms has been limited. Objectives: The purpose of the current study was to determine the effect of paraquat application on four nitrogen-fixing bacteria: Pantoea agglomerans, Rhizobium nepotum, Rhizobium tibeticum and Rhizobium radiobacter. Methods: Paraquat was applied as the sole source of carbon at a rate (0 g/L, 0.5 g/L, 1 g/L, 3 g/L, 6 g/L and 12 g/L). The effect of paraquat treatments was determined by agar diffusion method and the rate of the growth of bacterial colonies in each treatment. Results: In the agar diffusion method, the bacterial strains were inhibited by paraquat, in which the inhibition zone was wider with the increase of paraquat concentration; also, analysis of the Colony Forming Units (CFUs) mostly showed a declining in bacterial growth. In comparison with the control, the growth of the four strains was decreased by increasing the paraquat concentration. Comparing strains with each other, Pantoea agglomerans is the most resistant strain to paraquat. Conclusion: Our study has shown the impact of the irrational use of pesticide upon the beneficial bacteria in question. For that, the results of this research have a positive impact on the natural environment, which will have tangible social and economic impacts.

Ecotoxic response of Rhizobium sp. to the commonly used pesticides (paraquat and dichlorvos)

“…The response of Rhizobium to the two pesticides at 0.01 mg/L concentration, based on the tolerance indices obtained, did not differ significantly from one another (p≤0.05). The findings from the present study are supported by several similar studies which also established that paraquat, dichlorvos and other pesticides negatively influenced the growth of microorganisms in the receiving ecosystems (Nur et al, 2013;Maldani et al, 2018;Mazhari and Ferguson, 2018;Osadebe and George, 2022;Osadebe and Ubochi, 2022). Margino et al (2000), in their study on paraquat in peat land, reported that paraquat concentrations of 20 mg/kg had a strong inhibitory influence on the community dynamics of soil bacteria and fungi.…”

“…These xenobiotic compounds are well known to persist in soil and water systems impacting on the physical, chemical, and biological characteristics of these environments. Their fate is any ecosystem is largely contingent on their interaction with the native microbial communities (Maldani et al, 2018;Hamuda, 2020). Studies have shown that about 99.9 % of applied pesticides is lost to the receiving environment where it induces pesticide stress on non-target organisms in that environment due to its accumulation and persistence (Ahemad & Khan, 2011).…”

“…Though, certain microbial groups have been known to utilise pesticides as a source of carbon and energy, pesticides and their degradation by-products will often affect the cell densities, enzymatic activities, and physiology of exposed microorganisms within an ecosystem (Moawad et al, 2014;Ahemad & Khan, 2011). Maldani et al (2018) corroborate the toxicity of pesticides to groups of microorganisms and state that toxicity will often be most severe in the interval immediately following application or exposure.…”

Mirror proteorhodopsins

“…Pantoea is also known to form associations with humans and also a variety of hosts, including plants and insects 10 , 71 – 73 . Pantonea is also used in industry for bioremediation, herbicides degradation and other toxic products 74 – 77 . The microbe possesses plant growth-promoting capabilities and is used in agricultural applications 10 , 78 .…”

Pengaruh Aplikasi Herbisida Gromoxone 276 Sl (Larut) Terhadap Sifat Kimia Inceptisol

“…Namun, dalam beberapa kondisi herbisida dapat mempercepat terjadinya dekomposisi oleh aktivitas mikroba yang membantu penguraian bahan organik dari gulma yang telah mati sebagai bentuk korelasi posistif dalam bentuk adaptasi terhadap pemberian herbisida ke dalam tanah, sehingga C-organik dapat terjadi peningkatan akan tetapi tidak secara langsung dapat meningkatkan kandungan hara dan bahan organik tanah (Faqihhudin, 2013). bersifat beracun bagi beberapa mikroorganisme, tapi disisi lain juga bermanfaat bagi mikroorganisme lain sebagai sumber karbon, fosfor, atau nitrogen setelah terjadi degradasi (Maldani et al, 2018). Herbisida juga mengurangi proses biokimia yang diatur oleh mikroba tanah dan reaksi enzimatik yang berperan penting dalam menjaga atau meningkatkan kesehatan tanah, termasuk mineralisasi, dan transformasi bio terkait seperti dinamika nutrisi (nitrifikasi, denitrifikasi, dan amonifikasi), reaksi redoks, dan metanogenesis di dalam tanah (Meena et al, 2020).…”