Pseudomonas Exopolysaccharides: A Game Changer for Attaining Environmental Sustainability

Special Article: Phytoremediation

Austin Environ Sci. 2023; 8(3): 1100.

Pseudomonas Exopolysaccharides: A Game Changer for Attaining Environmental Sustainability

Sakshi Tewari*

1Department of Life Sciences, JC Bose University of Science and Technology, YMCA, India

*Corresponding author: Sakshi Tewari Department of Life Sciences, J.C. Bose University of Science and Technology, YMCA, NH-2, Sector-6, Mathura Road, Faridabad, Haryana 121006, India. Email: sakshitew@gmail.com; sakshi.tewari@jcboseust.ac.in

Received: October 03, 2023 Accepted: October 28, 2023 Published: November 04, 2023

Abstract

Exopolysaccharides (EPS) are the polymeric substance obtained from diverse species of the genera Pseudomonas for a variety of purposes. Recently, large focus have been given on isolation and characterization of EPS from diverse microorganisms employing various strategies, but very less attention have been given on the theme of harnessing EPS from the master microbe Pseudomonas and exploiting its multifaceted roles. Hence, the main essence of this review article is to emphasize protocols opted for EPS production, extraction and optimization, detailing its architecture, composition, mechanisms and genetic regulation. In the process it will also discuss various approaches used nowadays for novel usage of EPS bioformulations derived from Pseudomonas for plant growth promotion, stress amelioration, bioremediation and disease management in an eco-friendly and sustainable manner.

Keywords: Bioformulations; Biofilm; Biocontrol; Exopolysacchrides; Metabolites; Pseudomonas

Introduction

Polysaccharides commonly known as glycans are abundant in nature. These polysaccharides can be isolated from various living organisms including algae, plants, animals, fungi, protozoa and bacteria [75]. Nature of polysaccharide varies in terms of physical properties, chemical nature and biological attributes. Some bacterial cells are enclosed by a slimy polysaccharide layer, commonly known as the glycocalyx. Capsular polysaccharides are produced by those organisms in which glycocalyx are attached to the bacterial cell surface by covalent bonds. When polymer is very loosely bounded to the cell surface, it creates slime, and then it is referred as Exopolysaccharides (EPSs) [47,66]. The concept of EPS was first introduced by Sutherland in 2001. They are high-molecular-weight compounds, made from carbohydrate, proteins, DNA and some non-carbohydrate components including acetate, phosphate, pyruvate, succinate etc depending on the bacterial strains [23,101]. EPSs are broadly classified as homo-EPS and hetero-EPS. Homo-EPS are the one made up of only one mono-saccharide unit and hetero-EPS constitutes diverse mono-saccharides unit within it [114]. In nature, EPS is present in the form of capsular material in bacterial cell, and even obtained in the structure of slimes. Bacterial cells have multifaceted reasons for releasing EPS, some of them includes [1] maintaining cell growth under stress environment, [2] providing attachment during biofilm construction, [3] nutrient pool or carbon storage, [4] plant growth promotion and [5] biological control.

Hence, the main aim of this chapter is to highlight how this metabolite EPS can serve as a game changer in future for attaining environmental sustainability. The chapter will also focus on the multi-dynamic roles of EPS with reference to the genera Pseudomonas. In the process it will also discuss various strategies; protocols opted for EPS extraction, detailing its architecture, composition and genetic regulation. Novel usage of EPS bioformulations derived from Pseudomonas for plant growth stimulation and disease management has been also included (Figure 1). This chapter will especially help those researchers who are exploring the areas of EPS in conjugation with the genera Pseudomonas for developing multifaceted bioformualtions in order to attain environmental sustainability.

Pseudomonas: Versatile Bacteria

The genus Pseudomonas includes the most ingenious and ecologically remarkable group of bacteria on the planet earth. Pseudomonas, belongs to the class gamma (γ) Proteobacteria. At present, there are more than ten genera of Pseudomonadales that includes, Burkholderia, Caulobacter, Ralstonia, Sphingomonas, Stenotrophomonas, and Xanthomonas [21]. The family Pseudomonadaceae, contain the foremost genera Pseudomonas, that are principally gram-negative, rod-shaped, straight and slightly curved shaped bacterial cells with polar flagella [21]. They are generally aerobes or facultative anaerobes, positive for catalase and oxidase test, negative for vogues proskauer, indole and methyl red tests. Advance methods for identifying the genus Pseudomonas have been done on the basis of 16S rRNA sequencing technique, with universal primers like, forward primer Ps-for (20-mer [5'-GGTCTGAGAGGATGATCAGT-3']) and reverse primer Ps-rev (18-mer [5'-TTAGCTCCACCTCGCGGC-3']) (Widmer 1998). Diverse members of the genera Pseudomonas, are established in majority of the natural environments including freshwater, marine, terrestrial, extreme habitats etc. Some of the Pseudomonas species can form close intimate relations with plants and animals [91]. Diverse Pseudomonas species including Pseudomonas alcaligenes, Pseudomonas chlororapsis, Pseudomonas dimunita, Pseudomonas elongata Pseudomonas fluorescense, Pseudomonas putida, Pseudomonas syringae etc are comprehensively used in the area of agricultural and environmental microbiology for its various applications.

A number of major Pseudomonas applications includes: plant growth elongation, biological control, biofilm formation, antimicrobial metabolite production, quorum sensing, plant microbe synergistic interaction, chemotactic interaction, uptake, and catabolism of various plant secretions [92]. There are many reviews and book chapters available on the subjected cited above [41], but the role of Pseudomonas in EPS production and exploiting its novel applications is reported rarely. Generally various species of Rhizobia are regarded as EPS producers and much work has been cited on this topic [105,106]. But, throwing light on the role of EPS with reference to Pseudomonas is a new thought that needs to be explored.

EPS Production in Pseudomonas