Genotypes and Ecological Attributes of Methylotrophic Endophytes Isolated From Plant Phyllosphere.

The interactions between microbes and plants are highly complicated. Bacteria which show plant-growth promoting or plant-health promoting activities are commonly found in the rhizosphere and positively correlated with their plant host. But studies on the diversity of endophytic bacteria in plant phyllosphere and their functions are rare. This motivates us to perform a preliminary isolation and characterization of endophytes, especially methylotrophs from plant phyllosphere. In the present studies leaves originated from three kinds of trees were collected and surface sterilized. After grinding samples were serially diluted and plated on methanol containing medium to isolate methylotrophic endophytes. Bacterial identification was carried out based on 16S rDNA sequence analysis. Characteristics regarding plant growth promotion or organic compounds degradation of these isolates were analyzed. A total of 68 strains showing methanol utilization were obtained in the present work. These isolates belong to a wide range of genera including Acinetobacter, Arthrobacter, Aurantimonas, Bacillus, Pseudomonas, Rhizobium, and Stenotrophomonas. Most of the tested isolates can utilize glucose, the photosynthate produced within leaves as a sole source of carbon. Their methanol-utilizing ability may also play an important role in the colonization of leaves. Phosphate solubilization and siderophore production were recorded in some strains. Protease activities were commonly found in these bacteria, as can be seen from the utilization of skimmed milk. Isolates possessing other extracellular hydrolytic enzymes such as amylase, cellulase, ligninase, pectinase or xylanase may help in the degradation of plant cell wall and showed potential in the degradation of organic wastes. The nutrient requirement of these methylotrophic endophytes derived from plant phyllosphere will be studied in more detail to clarify their oligotrophic behavior, and these isolates with versatile traits might serve as superior biological agents used in agriculture.