Exploring the environmental traits and applications of Klebsiella variicola

Abstract

Klebsiella variicola has been found in various natural niches, alone or in association with other bacteria, and causes diseases in animals and plants with important economic and environmental impacts. K. variicola has the capacity to fix nitrogen in the rhizosphere and soil; produces indole acetic acid, acetoin, and ammonia; and dissolves phosphorus and potassium, which play an important role in plant growth promotion and nutrition. Some members of K. variicola have properties such as halotolerance and alkalotolerance, conferring an evolutionary advantage. In the environmental protection, K. variicola can be used in the wastewater treatment, biodegradation, and bioremediation of polluted soil, either alone or in association with other organisms. In addition, it has the potential to carry out industrial processes in the food and pharmaceutical industries, like the production of maltose and glucose by the catalysis of debranching unmodified oligosaccharides by the pullulanase enzyme. Finally, this bacterium has the ability to transform chemical energy into electrical energy, such as a biocatalyst, which could be useful in the near future. These properties show that K. variicola should be considered an eco-friendly bacterium with hopeful technological promise. In this review, we explore the most significant aspects of K. variicola and highlight its potential applications in environmental and biotechnological processes.

Keywords: Bioremediation; Nitrogen fixation; Wastewater treatment.

Fig. 1

Ecology of K. variicola, including properties, niches, and their association with industrial sustainable process. (a) K. variicola as a pathogen in plants, animals, and human. (b) Properties of N₂ fixing and denitrification. (c) Plants microbiota in and their contribution in N₂ assimilation and plant nutrition. (d) Bioremediation of contaminated soils and water, and participation in wastewater treatment. (e) Metal bioreductor/oxidized properties. (f) Hydrocarbon-biodegrading ability. (g) Participation in fermentation processes and the food and pharma industries

Fig. 2

Maximum likelihood phylogeny tree of nif-cluster nucleotide sequences was generated using Mega software v7.0.26 from 199 K. variicola genomes obtained from public GenBank/ENA databases. The Tamura-Nei model with discrete Gamma distribution was applied to model evolutionary rate. The tree was rooted using two K. quasipneumoniae nif-cluster operon nif. The circle indicates the origin of the isolates; green plants, red animals, brown insects, blue environmental, and yellow nitrogen fixation detected in vitro

Fig. 3

Beneficial impact and contribution of K. variicola in the environment and biotechnological processes