Coexistence among Epiphytic Bacterial Populations Mediated through Nutritional Resource Partitioning

Abstract

The levels of coexistence between Pseudomonas syringae and various nonpathogenic epiphytic species in the phyllosphere of beans (Phaseolus vulgaris) were assessed by using replacement series. The epiphytic species Pseudomonas fluorescens, Pantoea agglomerans, Stenotrophomonas maltophilia, and Methylobacterium organophilum were all capable of exhibiting higher levels of coexistence with P. syringae than was observed with a near-isogenic P. syringae strain pair. The ecological similarity of the epiphytes was estimated with niche overlap indices derived from in vitro carbon source utilization profiles. The level of coexistence of the epiphytes was inversely correlated with the ecological similarity of the strains. Hence, the level of coexistence between the epiphytes was proportional to the degree of niche differentiation, defined as the ability to utilize carbon sources not utilized by a competing strain. Comparisons of utilization profiles for groups of carbon sources (amino acids, organic acids, and carbohydrates) indicated the types of carbon sources for which the strains likely competed in the bean phyllosphere. P. fluorescens and P. syringae strains probably competed for most carbon sources. S. maltophilia and M. organophilum strains probably competed with P. syringae for most organic acids but few amino acids or carbohydrates. P. agglomerans strains probably competed with P. syringae for most amino acids and organic acids but few carbohydrates. A variable level of coexistence observed between P. agglomerans and P. syringae probably reflected the variability in abundance in the bean phyllosphere of the carbohydrates that P. agglomerans utilized exclusively.

Variation of Phyllosphere Microflora of Different Rice Varieties in Sri Lanka and its Relationship to Leaf Anatomical and Physiological Characters

“…These varieties should be investigated separately in a future study to determine the possible reasons for their divergent behaviour under the two different growing conditions. On the other hand, there is a wealth of experimental evidence to show that there could be significant variations in microbial density and diversity due to seasonal, physiological, environmental, spatial and temporal differences of the phyllosphere even within the same variety (O'Brien and Lindow 1989, Andrews 1992, Wilson and Lindow 1994, Kinkel et al 1996, Hirano and Upper 2000, Monier and Lindow 2004. Therefore, such variations of microbial density and diversity are acceptable under two different environmental conditions and for two different growing periods even among the same set of rice varieties.…”

Impact of Changes in Sugar Exudate Created by Biological Damage to Tomato Plants on the Persistence of Escherichia coli O157:H7

“…Available nutrients are rapidly used on the leaf surface by epiphytic microorganisms (Mercier and Lindow 2000). Microorganisms that use different sugars compared to other members of the phyllosphere might have greater potential for coexistence than microorganisms that share the same niche (Wilson and Lindow 1994). If enteric pathogens are not competing with the epiphytic flora for carbon and nitrogen sources, their survivability might be enhanced.…”

Thermo-responsive expression and differential secretion of the extracellular enzyme levansucrase in the plant pathogenic bacteriumPseudomonas syringaepv. glycinea

“…The extracellular enzyme Lsc (EC 2.4.1.10) is produced by various gram-negative and gram-positive bacteria and catalyzes synthesis of levan from sucrose by transfructosylation (Gross & Rudolph, 1987). Carbon compounds such as plant-borne sucrose are often limiting factors for bacterial growth on plant leaves (Wilson & Lindow, 1994). Since epiphytic bacterial population sizes on leaves depend on the amount of sugar present (Mercier & Lindow, 2000), bacterial saccharolytic enzymes such as Lsc or sucrase constitute a major metabolic pathway to utilize sucrose as the prime energy source.…”