Pantoea: A Versatile bacterial Candidate of Agricultural Importance

Abstract

Genus Pantoea is a diverse group of the family Enterobacteriaceae which inhabit various ecological niches. Various species of Pantoea are found associated with a diverse host range that include plants, animals, insects and humans. Besides this Pantoea spp. has been widely distributed in nature including water, soil, dairy products, meat and fish. It is commonly associated with plants as epiphyte or pathogen. Pantoea was first recognized as a genus about 25 years ago, but since then, approximately 20 species with a wide range of characteristics have been discovered. Identification of plant-pathogenic Pantoea species is difficult, due to the high degree of phenotypic similarity between species of this genus and related Enterobacteriaceae. Pantoea species are typically characterized based on colony morphology, physiological and biochemical tests, and in some cases, fatty acid analysis or quinone composition. These have a wide range of plant hosts where they live as nonpathogenic endophytes as well as epiphytes that colonize the leaves, stems and roots. In this perspective, some Pantoea strains can be beneficial to the plant host by providing growth promoting substances such as the plant-growth hormone indole-acetic acid (IAA), phosphate solubilization or nitrogen fixation. Number of Pantoea species are also involved in bioremediation of various pesticides and organic chemical compounds. This indicates the potential to degrade some recalcitrant and xenobiotic compounds. Some Pantoea strains also provide effective protection to plants against various bacterial and fungal diseases and post-harvest fruit rots. On the other hand, some of the species are recognized as a human pathogen and has led to controversy as limited documented cases of P. agglomerans bacteremia and infections have been reported. Most of the cases reported among immunocompromised patients or the pediatric population. Thus, Pantoea is a multifaceted bacterium that plays a significant role in agriculture as a plant growth promoter by producing hormone like IAA, inorganic pollutant degradation by producing potent enzymes and also protects some plants against pathogens by producing antibacterial and antifungal compounds. In some cases, these also cause diseases in human beings. Therefore, this genus is very important for studies. In this review, the industrial, agricultural as well as ecological significance of the genus Pantoea is emphasized.