First Advisor

Leonard Simpson

Term of Graduation

Fall 1994

Date of Publication

11-9-1994

Document Type

Thesis

Degree Name

Master of Science (M.S.) in Biology

Department

Biology

Language

English

Subjects

Iron -- Metabolism, Trichodesmium -- Caribbean Sea, Trichodesmium -- Sargasso Sea, Nitrogen -- Fixation

DOI

10.15760/etd.6778

Physical Description

1 online resource (x, 93 pages)

Abstract

This investigation tested the hypothesis that iron, as a micronutrient, will affect proteins in Trichodesmium and therefore affect nitrogen fixation. Changes in proteins that are a result of iron enrichment were compared to naturally occurring diel changes. Alterations in the iron protein of nitrogenase were compared to nitrogen fixation rates using the acetylene reduction technique. The observed changes in proteins were compared in Trichodesmium colonies from the Caribbean Sea and the Sargasso Sea.

Trichodesmium colonies were monitored for protein and iron content over a diel period on two cruises. The changes in protein and iron content in Trichodesmium colonies were variable but at times showed a cyclic diel pattern. Changes in protein bands on SDS-PAGE showed consistent changes in the banding pattern of a low molecular weight protein that responded to iron nutrition and time of day. These changes were similar to changes m the iron protein of nitrogenase which also responded to changes associated with iron nutrition and time of day. Trichodesmium appear to alter certain proteins which appear as changes in banding patterns in response to environmental factors such as nutrients, temperature and light.

My research shows that the pattern of modification of the iron protein of nitrogenase differs in colonies from the Caribbean Sea compared to those from the Sargasso Sea. The Caribbean Sea population in February had a clear pattern of active and inactive forms (day vs. night) of the enzyme. The Sargasso Sea population of Trichodesmium spp. had both forms of the enzyme at all times of the day during April and May when NO3 - is present in the euphotic zone due to recent mixing. These differences between the two populations may be due to different environmental conditions since the Caribbean Sea is permanently stratified, warmer and nutrient-depleted throughout the year. The Sargasso Sea undergoes seasonal breakdown of the thermocline during winter months, resulting in an injection of nitrate from deeper water, and minimum temperatures of 18°C.

Rights

In Copyright. URI: http://rightsstatements.org/vocab/InC/1.0/ This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).

Comments

If you are the rightful copyright holder of this dissertation or thesis and wish to have it removed from the Open Access Collection, please submit a request to pdxscholar@pdx.edu and include clear identification of the work, preferably with URL.

Persistent Identifier

https://archives.pdx.edu/ds/psu/28517

Download

Included in

Biology Commons

Share

COinS