Doctoral defence in Biology - Stephen Knobloch

Ph.D. student: Stephen Knobloch

Dissertation title: Host-microbe symbiosis in the marine sponge Halichondria panicea

Opponents: 
Dr. Detmer Sipkema, Associate Professor of Marine Microbial Ecology, Wageningen University & Research, The Netherlands
Dr. Ólafur Sigmar Andrésson, Professor of Genetics at Faculty of Life and Environmental Sciences at the University of Iceland

Department coordinator: Dr. Eva Benediktsdóttir, Associate Professor of Microbiology at the Faculty of Life and Environmental Sciences at the University of Iceland

Advisor: Dr. Viggó Þór Marteinsson, Professor at Faculty of Food Science and Nutrition at the University of Iceland and research group leader in Microbiology at Matís, Iceland

Doctoral committee: 
Dr. Ragnar Jóhannsson, Head of Aquaculture Division at the Marine and Freshwater Research Institute, Iceland

Chair of Ceremony: Dr. Snæbjörn Pálsson, Professor and Vice Head of the Faculty of Life and Environmental Sciences at the University of Iceland

Abstract:
Sponges (phylum Porifera) are the oldest extant lineages of the animal kingdom. Their close association with microorganism makes them suitable for studying early animal-microbe symbiosis and expanding our understanding of host-microbe interactions through conserved mechanisms. Moreover, many sponges and sponge-associated microorganisms produce bioactive compounds, making them highly relevant for the biotechnology and pharmaceutical industry. 

In this study, the microbial community of the marine sponge H. panicea from Icelandic waters was analysed through marker gene sequencing, genomics and bacterial cultivation. We showed that H. panicea from Icelandic water hosts a dominant bacterial symbiont across geographical locations and seasons whereas other bacteria are geographically and temporally transient. Functional genomic analysis of the dominant symbiont, for which we propose a candidate status with the name “Candidatus Halichondribacter symbioticus”, showed a lack of regulatory genes in line with its obligate symbiotic lifestyle. In addition, it is enriched in sponge symbiont specific gene families related to host-symbiont interactions and defence. Despite the presence of a putative bacteriocin gene cluster, “Ca. H. symbioticus” does not appear to be the source of other bioactive secondary metabolites in this sponge. 
The H. panicea – “Ca. H. symbioticus” system represents a promising model for studying early animal-microbe symbiosis and the results from this study lay the groundwork for future studies exploring these interactions.

About the doctoral candidate:

Stephen Knobloch was born in 1987 in Toronto, Canada. In 2010, he graduated from the University of Applied Sciences Bremerhaven, Germany with a BSc in in Maritime Technologies and a specialization in Marine Biotechnology. He continued his studies at the University of Rostock, Germany, and graduated in 2013 with a MSc in Aquaculture.
In 2014, he started the doctoral program at the University of Iceland as a Marie-Curie PhD fellow in the EU project BluePharmTrain. Stephen taught courses in Advanced Food Microbiology in the fall semester of 2016-2018 and manages the nationally funded research project FishGutHealth since 2017.

Stephen currently lives in Reykjavik with his wife Rebecca and two children, Sascha, born in 2014 and Nora, born in 2017.

Event on Facebook