~ 91 ~ WWJMRD 2022; 8(11): 91-94 www.wwjmrd.com International Journal Peer Reviewed Journal Refereed Journal Indexed Journal Impact Factor SJIF 2017: 5.182 2018: 5.51, (ISI) 2020- 2021: 1.361 E-ISSN: 2454-6615 Ariel de Figueiredo Nogueira Mesquita, João Moreira de Matos Neto Biotechnology Student (undergraduate) – Department of Biochemistry and Molecular Biology - Federal University of Ceará – Fortaleza - Brazil. Leonardo Lima Bandeira Graduate Student in Ecology and Natural Resources – Federal University of Ceará – Fortaleza - Brazil Fernando Gouveia Cavalcante PhD in Ecology and Natural Resources – Federal University of Ceará – Fortaleza - Brazil Suzana Claudia Silveira Martins, Claudia Miranda Martins Microbiology Professor at Biology Department – Laboratory of Environmental Microbiology – Federal University of Ceará – Fortaleza – Brazil. Correspondence: Ariel de Figueiredo Nogueira Mesquita Biotechnology Student (undergraduate) – Department of Biochemistry and Molecular Biology - Federal University of Ceará – Fortaleza - Brazil. arielmesquita26@alu.ufc.br Amylase-Producing Actinobacteria Facilitate Rhizobia Growth in a Culture Medium with Starch Ariel de Figueiredo Nogueira Mesquita, Leonardo Lima Bandeira, Fernando Gouveia Cavalcante, João Moreira de Matos Neto, Suzana Claudia Silveira Martins, Claudia Miranda Martins Abstract Plant growth-promoting rhizobacteria (PGPR) are microorganisms that act in the production of metabolites that confer advantages for the growth and development of the plant, receiving in exchange sources of carbon and energy. Two classic examples of PGPR are rhizobia, which act in the bioavailability of nitrogen, and actinobacteria, which perform numerous functions such as production of phytohormones, antibiotics, and solubilization of phosphate and potassium. To establish this microbiota, the plant releases carbohydrate-rich exudates that not only serve as a carbon source for microorganisms, but also determine which microorganisms can colonize its rhizosphere. This study evaluated how amylase-producing actinobacteria are able to allow rhizobia growth without this enzymatic activity when co-inoculated in a culture medium that has starch as the sole carbon source. Since starch is a carbohydrate like those released in exudates, it is inferred that this ability to facilitate growth in vitro would be important in stimulating rhizobia growth in the rhizosphere and, consequently, nitrogen fixation. Ten actinobacteria and seven rhizobia were used, of which we obtained 12.86% of positive results. This cooperation exemplifies another case of substrate cross- feeding, paving the way to further in vitro and in vivo studies of interbacterial interactions, as well as to the prospect of biofertilizers. Keywords: Bacterial ecological interactions; Bioinoculant; Cross-Feeding; PGPR; Streptomyces. 1. Introduction Microorganisms play numerous ecological roles in soil, such as changing the spatial distribution and bioavailability of nutrients [1] . Bacteria beneficial to plants are traditionally known as plant growth promoting rhizobacteria (PGPR) and act in the mobilization of nutrients in the soil, production of growth regulators, phytohormones, solubilization of phosphate and potassium, and protection against phytopathogens [2] . Plant growth, productivity, and health rely on the microbial community associated with it, so the plant shapes the composition of the rhizospheric microbiota via rhizosphere feedback. Exudates are rich in carbohydrates, amino acids, organic acids, flavonoids, growth factors, enzymes, among others, which vary from plant to plant due to genetic and environmental factors, and are capable of selecting and stimulating microbial growth [3, 4, 5] . In association with factors such as soil type and pH, exudates determine the nature of the local microbiota [6] . The release of flavonoids from roots attracts bacteria known as rhizobia. These bacteria are the most classic example of PGPR due to its capacity of forming symbiotic nodules in the roots of legumes. There, they perform biological nitrogen fixation, which is a process responsible for making this nutrient bioavailable to the plant [7] . Exudates also attract other PGPRs such as actinobacteria. These bacteria stimulate plant growth, antagonize phytopathogens, improve nutrient availability, and produce phytohormones such as auxins and gibberellins [8] . Outside the rhizospheric environment, actinobacteria also show great biotechnological value for the production of antibiotics, insecticides, herbicides, immunomodulators, and enzymes such as cellulases, xylanases, pectinases, proteases, chitinases and amylases [9] . World Wide Journal of Multidisciplinary Research and Development (November-2022)