Moreover, the same Bacteroidetes, Mycoplasma, Phyllobacteriaceae, and in particular Flavobacteriaceae bacteria, were detected in several Bryopsis samples collected hundreds of kilometers apart. This apparent spatial stability of the Bryopsis-bacterial endobiosis, however, raises the question whether these endophytes are a subset of the free-living bacterial community or whether there is some specificity click here towards the Bryopsis host. Although the distinctiveness between free-living and macroalgal-associated bacterial communities is well established
[4–8], the extraordinary morphological and physiological characteristics of the Bryopsis host must have implications for the specificity of its bacterial endophytes. Bryopsis is a marine siphonous macroalga composed of a single, tubular shaped cell which contains multiple nuclei and chloroplasts in a thin cytoplasmic layer surrounding a large central vacuole . While an organism composed of MEK inhibitor a giant, single cell would be prone to damage, siphonous macroalgae possess an intricate defense p38 MAPK phosphorylation network that operates at various levels [7, 10]. In Bryopsis, for example, the metabolite kahalalide F, which shows in vitro therapeutic activities, protects the alga
from fish predation . Even if damage does occur, a complex, multistep wound response is triggered [10, 12] to which Bryopsis algae add a surprisingly feature, i.e. the formation of protoplasts . These protoplasts are membraneless structures that can survive in seawater for 10-20 minutes. Subsequently, membranes and a cell wall are synthesized de novo surrounding
each protoplast, which then develop into new Bryopsis plants. This not only suggests learn more Bryopsis can exist – at least transiently -without a cell membrane, it also questions the nature of the association between the algal host and the endophytic bacterial communities present. Are these bacteria Bryopsis-specific, obligate endophytes (specialists) or are they rather generalists (facultative endogenous bacteria) which are repeatedly acquired from the local environment (epiphytic communities and/or surrounding sea water)? To address this issue, we evaluated the temporal stability of the endobiotic bacterial communities after prolonged cultivation of Bryopsis isolates. We also examined the diversity of the epiphytic and surrounding water bacterial communities of five Bryopsis isolates in culture using the DGGE technique and subsequently compared these DGGE profiles with previously obtained DGGE banding patterns of Bryopsis endophytic bacterial communities . Methods Sample collection and DNA extraction Bryopsis hypnoides (MX19 and MX263) and Bryopsis pennata var. leprieurii individuals (MX90, MX164 and MX344) were collected in February 2009 at five different sites along the Mexican west coast . Living algal samples were transferred to the laboratory and unialgal Bryopsis cultures were formed by repeatedly isolating clean apical fragments.