Bacterial Colonization of the Phyllosphere of Mediterranean Perennial Species as Influenced by Leaf Structural and Chemical Features

Abstract

In this study, we assessed various leaf structural and chemical features as possible predictors of the size of the phyllosphere bacterial population in the Mediterranean environment. We examined eight perennial species, naturally occurring and coexisting in the same area, in Halkidiki (northern Greece). They are Arbutus unedo, Quercus coccifera, Pistacia lentiscus, and Myrtus communis (evergreen sclerophyllous species), Lavandula stoechas and Cistus incanus (drought semi-deciduous species), and Calamintha nepeta and Melissa officinalis (non-woody perennial species). M. communis, L. stoechas, C. nepeta, and M. officinalis produce essential oil in substantial quantities. We sampled summer leaves from these species and (1) estimated the size of the bacterial population of their phyllosphere, (2) estimated the concentration of different leaf constituents, and (3) studied leaf morphological and anatomical features and expressed them in a quantitative way. The aromatic plants are on average more highly colonized than the other species, whereas the non-woody perennials are more highly colonized than the woody species. The population size of epiphytic bacteria is positively correlated with glandular and non-glandular trichome densities, and with water and phosphorus contents; it is negatively correlated with total phenolics content and the thickness of the leaf, of the mesophyll, and of the abaxial epidermis. No correlation was found with the density of stomata, the nitrogen, and the soluble sugar contents. By regression tree analysis, we found that the leaf-microbe system can be effectively described by three leaf attributes with leaf water content being the primary explanatory attribute. Leaves with water content >73% are the most highly colonized. For leaves with water content <73%, the phosphorus content, with a critical value of 1.34 mg g(-1) d.w., is the next explanatory leaf attribute, followed by the thickness of the adaxial epidermis. Leaves higher in phosphorus (>1.34 mg g(-1) d.w.) are more colonized, and leaves with the adaxial epidermis thicker than 20.77 microm are the least colonized. Although these critical attributes and values hold true only within the Mediterranean ecosystem studied and the range of observations taken, they are important because they provide a hypothesis to be tested in other Mediterranean ecosystems and other biomes. Such comparative studies may give insight as to the general properties governing the leaf-microbe system.

Both Leaf Properties and Microbe-Microbe Interactions Influence Within-Species Variation in Bacterial Population Diversity and Structure in the Lettuce ( Lactuca Species) Phyllosphere

“…Levels of bacterial epiphytic phyllosphere colonization have been reported to range from 10 1 to 10 8 CFU g Ϫ1 between different plant genera (18,20,53). Total bacterial colonization of the lettuce phyllosphere in this study ranged from 4 ϫ 10 5 to 5 ϫ 10 6 CFU g (FW) Ϫ1 , which is comparable to the levels of epiphytic lettuce colonization (18).…”

“…The microbial population already resident in the phyllosphere is also likely to impact significantly on the ability of incoming organisms to successfully colonize the leaf surface. Variation in such resident populations between different plant species has been attributed to differences in a range of plant physiochemical characteristics, including the water and phosphorus contents of the leaves, levels of phenolic compounds (which may be inhibitory toward many bacteria), and leaf and mesophyll thickness (53). All of these plant characteristics have a genetic basis.…”

Phyllosphere Bacterial Population of Woody Species in Subtropical Forest at Shivapuri-Nagarjun National Park, Nepal Himalaya

“…Leaf age and leaf surfaces also influence the abundance of phyllosphere bacterial populations [15]. Concomitant with this, it was reported that bacterial abundance on the phyllosphere were negatively correlated with the concentration of phenolic substances, thickness of total leaf, mesophyll thickness and thickness of leaf cuticle [42].…”

Establishment of Antifungal Phyllospheric Bacteria in Potato (Solanum tuberosum L.)

“…The epiphyte population is dominated by bacteria which can be found in numbers ranging from 10 5 to 10 7 cells/g of plant material (Yadav et al, 2005). Artur et al, (2015) (Table 2).…”