13 - PROKARYOTIC DIVERSITY BIOL 4125 SPRING 2009 LECTURE 13...

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon
PROKARYOTIC DIVERSITY BIOL 4125 SPRING 2009 LECTURE 13 The Phototrophs Part 2
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
There are 5 major morphological types of cyanobacteria Unicellular Colonial Filamentous Filamentous heterocystous Filamentous branching Gloeothece Dermocarpa Oscillatoria Anabaena Dermocarpa Phylogenetically, cyanobacteria group along morphological lines in most cases. Filamentous heterocystous and nonheterocystous species form distinct groups, as do the branching forms. However, unicellular cyanobacteria are phylogenetically highly diverse, with different representatives showing phylogenetic relationships to different morphological groups.
Background image of page 2
Gas vesicles in Anabaena and Microsystis Thylakoid membranes in Synechococcus lividus
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Structural differentiation in filamentous cyanobacteria In filamentous cyanobacteria, fragmentation of the filaments often occurs by formation of hormogonia, which break away from the filaments and glide away. In some species, resting spores or akinetes are formed. These are environmentally resistant structures that protect the organism during periods of darkness, drying, or freezing. These cells have thick outer walls and when conditions are favorable, the outer wall is broken down followed by outgrowth of a new vegetative filament.
Background image of page 4
sources of nitrogen fixation in heterocystous cyanobacteria Gene arrangement in vegetative cell Gene arrangement in heterocyst Nitrogenase is coded by nifD and nifK . When mapped in vegetative cells, the nifD and nifK genes were located 11 kb away, but need to be produced in equimolar amounts. When the DNA from heterocysts was mapped, there was no intervening DNA between nifD and nifK . http://www.mun.ca/biochem/courses/3107/Topics/Site_specific_Recomb.html Further research demonstrated that heterocyst differentiation requires a site-specific recomb- ination event to excise this intervening element. The recombination is catalyzed by a protein which acts at two directly repeating 11 bp sequences within the nifD gene (red triangles). Since this initial discovery, two additional DNA rearrangements have been characterized.
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 6
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 08/04/2009 for the course BIOL 4125 taught by Professor Christner during the Spring '08 term at LSU.

Page1 / 15

13 - PROKARYOTIC DIVERSITY BIOL 4125 SPRING 2009 LECTURE 13...

This preview shows document pages 1 - 6. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online