Day 7: How and why? The Chan Lab investigates

A culturing station in the lab, with hand-knitted representation of Mariprofundus, a kind of Zetaproteobacteria that produces twisted iron oxide stalks (pink part) trailing behind the live cell (grey part). Knitting credit: Margo Haywood.

A microbe culturing station in the lab, with hand-knitted representation of Mariprofundus, a kind of Zeta that produces twisted iron oxide stalks (pink part) trailing behind the live cell (grey part). Knitting credit: Margo Haygood.

On this cruise to Loihi Seamount, the Chan lab–Prof. Clara Chan and PhD student Sean McAllister of U. Delaware, with collaborating post-doc Shingo Kato of RIKEN–is focused on the detailed evaluation of the structure and function of iron and sulfur oxidizing microorganisms (aka, they use iron and/or sulfur as their food source). We have spent many years at Loihi looking at the question of ‘who is there?’, and we have been able to sample these communities at increasingly smaller spatial scales. This trip, however, the Chan Lab focus is to connect the who with the how and why.

Shingo checks out Zetas under the microscope.

Shingo checks out Mariprofundus under the microscope.

How are they oxidizing iron; which genes are necessary for iron oxidation by the Zetaproteobacteria? We have some ideas about which genes are responsible for iron oxidation in acidic and near neutral freshwater systems, but so far there is very little know about iron oxidation in the marine environment.

Why is it that different Zetaproteobacteria form different iron oxide structures? Can we link these organisms to a specific niche such as a dependence on a particular chemical profile or a preferred location within the mat?

A micrograph of twisted iron oxide stalks produced by Zetas. Some Zetas produce a Y-shaped stalk instead; we could show you a micrograph of this different morphotype, but instead we’ll use interpretative dance.

A micrograph of twisted iron oxide stalks produced by Zetas.
Some Zetas produce a Y-shaped stalk; we could show you a micrograph of this different morphotype, but instead we’ll use interpretative dance.

We will try to answer these questions with various microbe cultivation strategies (including the cultivation of iron oxidizers that can also oxidize sulfur), in addition to active RNA transcript sequencing and the observation of mat formation in microslide enrichments.

–Sean McAllister, U. Delaware

Photo credits: Sean McAllister (top and middle), Clara Chan (bottom micrograph)

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