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Research topics

 

Microbial diversity and functions at unusual habitats

 

Innovative instruments for aquatic microbiology

 

Microplastics in marine habitats

A notable part of plastic waste ends up in the global oceans, e.g. estimated for the year 2010 to amount to 4.8 – 12.7 million metric tons (Jambeck et al., 2015). Plastics have been detected everywhere in the marine system, with particular high accumulation rates in the ocean gyres (Cozar et al., 2014). Our research focuses on microplastics, particles < 5mm. Primary microplastics are small particles in consumer care products, clothes fibers or virgin pre-production resin pellets. Secondary microplastics are formed in the environment by fragmentation of larger plastic items.

It is known that microplastics enter the marine system, for instance via sewage treatment plants, industrial spillage or accidental dropping. The consequences of this pollution for the marine foodweb, however, have not been understood yet. In particular, the role of microbial communities, which colonize microplastics, represents a research gap. First studies on the topic suggest microplastics in the ocean to be colonized by diverse pro- and eukaryotic microorganisms (Zettler et al., 2013, Oberbeckmann et al., 2014). In this context, bacteria of the genus Vibrio deserve special attention. This group of microorganisms harbors several pathogenic species and is further known to associate with biota and form biofilms on marine surfaces. Vibrio bacteria already have been found on plastics in seawater and at beaches (Zettler et al., 2013, Quilliam et al., 2014).

With our research we aim at i) determining the abundances, sources and sinks of microplastics in the marine system, ii) unraveling the diversity and structure of microbial communities associated with microplastics, and iii) exploring the potential of microplastics to serve as vector for pathogenic bacteria.

Microplastics research in the working group Environmental Microbiology is based on the Leibniz-funded consortium project called MikrOMIK, which deals with microplastics in the Baltic Sea. Furthermore, we sampled microplastics during a cruise with the MS Merian in the Sargasso Sea. Based on these samples we will explore microbial biofilms on microplastics in the North Atlantic Garbage Patch. In the PlasticSchool project, the findings were transformed into comprehensible and pedagogically valuable school modules. The resulting teaching units can be carried out independently by teachers and are available for all grades.

In the year 2017, further microplastic projects have been started, based on the findings of MikrOMIK. They are mainly concerned with the sources and sinks of microplastics in the Baltic Sea and its catchment area. The MicroCatch_Balt project deals with the sources and sinks of microplastics in the Warnow catchment area. The aim is to investigate how much microplastic enters the Baltic Sea via a typical river basin. BONUS MICROPOLL deals holistically with the topic of microplastc in the Baltic Sea, including associated pollutants and microorganisms. The project of the IOW includes the determination of a) the MP abundance and composition in water, sediments and beaches of the Baltic Sea, b) the retention time of MP in the ecosystem, and c) the vector function of MP for microorganisms. In the PLASTRAT project, the IOW is investigating the input of microplastic deriving from sewage treatment plants and sewage sludge. Together, all these projects form the theme cluster' plastic in the oceans'.

Vibrios and its phages in marine habitats

Bacteria of the genus Vibrio are ubiquitous members of marine ecosystems. They occur in coastal, estuarine and brackish waters as well as sediments, often in association with higher organisms. Increased water temperatures lead to both, increased population densities of Vibrio spp. and the occurrence of potential pathogenic Vibrio species, which cause infections in (immunodeficient) humans (Ruppert et al. 2004). An infection with V. vulnificus, for instance, can result in sepsis with potential fatality. In recent years, multiple cases of severe wound infection and fatalities caused by V. vulnificus were reported in the Baltic Sea area.

Within the scope of a monitoring program of the state Mecklenburg-Vorpommern, high Vibrio abundances were detected. Presumably, infections caused by members of the genus Vibrio will increase further in the light of climate change (Baker-Austin et al. 2013).

That’s why we are interested in the diversity of Vibrio populations in coastal areas. Within the project Vibrio – MV we will explore the reservoirs and diversity of Vibrio populations, focusing on the species V. vulnificus, within the coastal environment of Mecklenburg-Vorpommern.

Bacteria of the genus Vibrio were also found in biofilms covering particles of microplastic (Zettler et al. 2013). Their potential role within these biofilms will be investigated in the project MikrOMIK.

Our earlier research activities about phage host interactions (Wolf et al., 2003, Wolf et al., 2004, Jost & Wiese, 2013) are now focussed on such of bacteria of the genus Vibrio (Sun et al., 2008, Yu et al., 2013).

Within the joint research project ECOLOC we will investigate the differences within the populations of bacteria of the genus Vibrio and their phages in aquaculture systems at the coast of Hainan (China) as well as in the adjacent coastal areas. One aspect of these investigations will be the potential application of these phages within a phage therapy for disease control in these aquaculture systems.