Microhabitat heterogeneity across leaves and flower organs promotes bacterial diversity

Abstract

Eukaryote-associated microbiomes interact with their hosts in multiple manners, thereby affecting the hosts' phenotype, physical condition and behaviour. In plants, bacteria have numerous functions, with variable net effects, both in natural and agricultural systems. However, information about the composition and diversity of the bacterial communities associated with different aboveground plant organs, particularly flowers, is lacking. In addition, the relative effects of microhabitat and environmental conditions on community establishment require further attention. Here, using culture-independent methods, we determine that leaves and three floral microhabitats (nectar, stamina and styles) of Metrosideros polymorpha (Myrtaceae), a tree endemic to Hawai'i, host unique indicator communities composed of relatively abundant bacterial taxa. These indicator communities are accompanied by a large number of ubiquitous or rare bacteria with lower abundances. In our study system, the strong effect of microhabitat filtering on plant-associated community composition and bacterial richness and diversity strongly exceeds the influence of environmental effects such as precipitation, altitude, substrate age and geographic distance. Thus, the bacterial richness of aboveground plant organs is strongly underestimated when only one microhabitat, e.g. leaves, is considered. Our study represents a first step towards a comprehensive characterization of the distribution, composition and underlying factors, of plant bacterial communities, with implications for future basic and applied research on plant health, pollination and reproduction.

Metabarcoding of Bacteria Associated with the Acute Oak Decline Syndrome in England

“…Similar to studies of other plant organs, Proteobacteria dominated the communities associated with oak tissue and included the presence of Bacteroidetes and Firmicutes [6,13,15,19,[78][79][80][81]. Interestingly, Juncker et al [6] identified a member of the Gammaproteobacteria (Enterobacteriaceae) as dominant in stamina and styles whereas a member of the Pseudomonadaceae was identified as dominant in the oak microbiome.…”

“…Both sites had considerably lower OTU numbers and the phylogenetic diversity was lower than in the other three sites ( Table 2). The number of taxa detected at all sites was generally comparable to the phyllosphere microbiome consisting of several hundred or less taxa [6,[13][14][15][16].…”

“…The procedure was carried out on the 4 June 2015. Removal of OTUs assigned to chloroplasts, chlorophyta, mitochondria, archaea and sequences unassigned at kingdom level were removed from the dataset as described previously [6]. We observed a high variation in sequence number obtained for different samples as described previously [48].…”

“…Interestingly, Juncker et al [6] identified a member of the Gammaproteobacteria (Enterobacteriaceae) as dominant in stamina and styles whereas a member of the Pseudomonadaceae was identified as dominant in the oak microbiome. Our finding is in line with findings from Ottesen et al [7], who also detected dominance by members of the Pseudomonadaceae and Micrococcineae on tomato fruit samples.…”

The presence of aggressive ants is associated with fewer insect visits to and altered microbe communities in coffee flowers

“…We sampled microbial communities on floral stigmas and in nectar of coffee flowers, which are open between 2-5 days (Jiménez-Castano & Castillo-Zapata 1976;Free 1993). We sampled floral nectar and stigmas because they likely differ in suitability for microbial growth and may host different microbial communities (Junker & Keller 2015). Nectar acts as a strong biological filter, and only a phylogenetically restricted subset of microorganisms with particular adaptations has been found to attain high abundance in this environment (e.g.…”