Publication Date:
2022-05-25
Description:
Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 2008.
Description:
An increased understanding of heterotrophic bacterial strategies for acquiring nutrients
and trace elements is critical for elucidating their impact on biogeochemical cycling in
the ocean. It is estimated that iron is a limiting nutrient for phytoplankton growth in over
30% of the open ocean, but still little is known about bacterial strategies for iron
acquisition. Siderophore (Fe ligand) production by bacteria may play a major role in
influencing the bioavailability of iron in the ocean. Despite the importance of
siderophores in the environment, only limited information from a select group of bacteria
is available. On a cruise through the Costa Rica Dome (CRD) upwelling region in July
2005, a library of 867 isolates from five depth profiles inside and outside of the dome
was obtained and screened for siderophore production using the Chrome Azurol-S (CAS)
assay. Phylogenetic affiliation of 134 isolates was determined by sequencing the 16s
rDNA gene, and determined that gamma proteobacteria such as Alteromonas,
Pseudoalteromonas, Halomonas, and Marinobacter dominated the collection, while
alpha-proteobacteria such as Roseobacter were also represented. The isolates obtained
from stations in the CRD showed greater siderophore-producing capabilities between
55m and 100m while strains isolated from outside the CRD had shallower peak (~8-35m)
production. Functional group determination showed that hydroxamate production
dominated from 50-150m, while hydroxamate and catechol production is roughly equal
in shallower waters. By characterizing the siderophores produced by these isolates and
determining the genetic make-up of the population, these findings further our
understanding of how heterotrophic microbes affect biogeochemical processes and the
competitive nature of nutrient acquisition.
Description:
I am grateful to my funding sources, National Science Foundation grants BO OCE-
0352241 "The Effect of Iron Bioavailability on Synechococcus diversity from a HNLC
region to the Costa Rica upwelling dome" and CO-OCE-0452883 "Interactions of Cobalt
and Iron with in situ Cyanobacterial Physiology in the South Atlantic and the Benguela
Upwelling Region", the National Science Foundation Graduate Research Fellowship, and
the Academic Programs office.
Keywords:
Siderophores
;
Heterotrophic bacteria
;
Knorr (Ship : 1970-) Cruise KN182-50
Repository Name:
Woods Hole Open Access Server
Type:
Thesis
Format:
application/pdf
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