Scanning electron microscopy (SEM) was employed for the investigation of microorganisms living in marine sand sediments. Epifluorescence, as well as sediment analyses, gave further data on the parameters of the sediment samples.
SEM revealed a correlation between the site and density of bacterial colonization and the microtopography of the individual sand grains.
Sand grains with a medium roundness showed the greatest density of bacterial colonization. Protected surface sites were favored in the colonization process. The mode of bacterial attachment varied; mostly the barren sand grain surface was colonized. However, bacteria were also observed close to or within detritus or attached to diatoms. Many of the attaching bacteria observed were found to produce polymer strands.
In some cases special structures were discovered which could serve bacterial attachment. Entire colonies attached by means of polymer nets, and disc-shaped bacteria were observed.