Plastics become rapidly colonized
by microbes when released into
marine environments. This microbial communitythe Plastispherehas
recently sparked a multitude of scientific inquiries and generated
a breadth of knowledge, which we bring together in this review. Besides
providing a better understanding of community composition and biofilm
development in marine ecosystems, we critically discuss current research
on plastic biodegradation and the identification of potentially pathogenic
“hitchhikers” in the Plastisphere. The Plastisphere
is at the interface between the plastic and its surrounding milieu,
and thus drives every interaction that this synthetic material has
with its environment, from ecotoxicity and new links in marine food
webs to the fate of the plastics in the water column. We conclude
that research so far has not shown Plastisphere communities to starkly
differ from microbial communities on other inert surfaces, which is
particularly true for mature biofilm assemblages. Furthermore, despite
progress that has been made in this field, we recognize that it is
time to take research on plastic–Plastisphere–environment
interactions a step further by identifying present gaps in our knowledge
and offering our perspective on key aspects to be addressed by future
studies: (I) better physical characterization of marine biofilms,
(II) inclusion of relevant controls, (III) study of different successional
stages, (IV) use of environmentally relevant concentrations of biofouled
microplastics, and (V) prioritization of gaining a mechanistic and
functional understanding of Plastisphere communities.
How oligotrophic marine cyanobacteria position themselves in the water column is currently unknown. The current paradigm is that these organisms avoid sinking due to their reduced size and passive drift within currents. Here, we show that one in four picocyanobacteria encode a type IV pilus which allows these organisms to increase drag and remain suspended at optimal positions in the water column, as well as evade predation by grazers. The evolution of this sophisticated floatation mechanism in these purely planktonic streamlined microorganisms has important implications for our current understanding of microbial distribution in the oceans and predator–prey interactions which ultimately will need incorporating into future models of marine carbon flux dynamics.
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