Role of plant-associated microbes in plant health and development: the case of the Serratia genus

The genus Serratia, a member of the family Enterobacteriaceae, is found in diverse ecological environments. Recently, Serratia has emerged as a multifaceted contributor to plant growth promotion and defense against plant diseases and insect pests. This review examines the mechanisms by which Serratia spp. induce plant growth and alleviate both abiotic and biotic stresses. Their seamless integration within the plant ecosystem allows Serratia spp. to produce quorum-sensing molecules, N-acyl homoserine lactones (AHLs), facilitating colonization of plant tissues and capitalizing on nutrition from plant exudates. This intricate web of communication enables Serratia to produce phytohormones and break down essential nutrients from the soil for plant uptake. When confronted with ecological competitors, many Serratia strains showcase remarkable adaptability by producing a diverse array of hydrolytic enzymes and antibacterial, antifungal, or insecticidal compounds, effectively controlling harmful bacteria, fungi, and insect pests. Furthermore, beneficial Serratia strains also use induced systemic resistance (ISR) and tolerance (IST) to alleviate biotic and abiotic stresses, respectively. Various agricultural applications of Serratia include the direct use of bacterial cells for seed coating, foliar spraying, and soil inoculation, or the application of their bioactive compounds alone or in combination with other materials on various plant parts. These efforts aim to bolster plant health, curb diseases, and manage pest populations. Despite promising applications, there have been reports of opportunistic pathogenicity in plants and animals. Therefore, several safety approaches and the use of virulence factor mutant strains should be considered. The trend toward the application of Serratia in agriculture is expected to continue.