Dr. Johan Wikner’s Network

DR. JOHAN WIKNER, PROFESSOR AND DIRECTOR FOR THE UMEÅ MARINE RESEARCH CENTRE, UMEÅ UNIVERSITY

Prokaryotic maintenance energy: Metabolic strategies to maximize fitness:

Prokaryotes lining in natural environment are often exposed to famine leading to low growth rates. For aquatic bacteria this has been shown to impose a higher share of maintenance energy. This will lead to a different control of aquatic respiration relevant for ecosystem effects like development and management of hypoxia. For the prokaryotic cell the higher energetic need for maintenance activities may include foraging for nutritious substrates, synthesis of storage material of elements in excess, chemotaxis and also energy spilling reactions. What activities that are causing the elevated maintenance respiration is unknown and therefore the ecological fitness it provides. Dominating activities is also possibly varying with environment and prokaryote. Survival and foraging for nutrients at famine conditions is probably the most common living conditions for prokaryotes in the Ocean. This growth state is therefore crucial to understand in the context of bacterial ecology on Earth and global energy and carbon flows.

We address the overall questions 1) what metabolic activities or morphological transformations cause the elevated maintenance respiration? 2) How do the maintenance respiration provide an increased fitness for the prokaryote? 3) Are prokaryotes prone to enhanced genetic adaptation or evolution at famine and high maintenance cost?

The activities and morphological transformations are studied in both continuous cultures and field samples. For the initial experiments, in house isolates from a sub-arctic estuary of the taxa Flavobacterium sp. and Marinomonas sp. are used. Prokaryotic growth rate is controlled by the dilution rate in continuous cultures, and measured by radiolabelled substrates in the field. Bacterial activity is investigated by measuring gene expression and elemental ratio shift by electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS). Respiration is measured by optodes using dynamic luminescence technique. The work is conducted at Umeå Marine Sciences Center and on board research vessels at Sea.

This basic science project is also connected to bioremediation of polluted coastal recipients and the use of bacteria as indicators in environmental monitoring and management.

Key words: prokaryote, maintenance, respiration, metabolism, fitness.

Themes: Primarily (2) Functional diversity and (3) Microbial interactions and evolution

Dr. Ashish Verma, Post-doc

I am working on understanding the adaptation mechanisms of Arctic prokaryotes at low growth rates and higher maintenance respiration. These mechanisms will be investigated using chemostat experiments, mesocosm platforms and the Arctic expedition.

Keywords:

Chemostat, Mesocosm, Respiration, Microscopy, Omics

Themes:

1,2