Topic 3 Study Questions Flashcards
Some cyanobacteria form large mound-shaped structures: (a)
What are they called? (b) What are they made of? (c) What are
the characteristics of the environment where modern formations
are found?
They are called stromatolites
Layered calcareous structures of cyanobacteria
Generally marine environments, hypersaline and some low latitude lakes
Describe the different types of cyanobacteria thallus structure
Unicells
Colonies
Unbranched Filaments
Unbranched forms with specialized cells
Aggregations of multiple trichomes in a common sheath
False-branched forms
True-branched forms
Draw a diagram with the different layers of the cyanobacterial
cell wall
Describe the 3 known modes of motility in cyanobacteria.
Swimming:
surface motility protein
no effect of light
In Synechococcus in open ocean
Gliding:
Extrusion of mucilage through pores in cell wall, or extension of very fine protein fibrils
Light affects direction and speed
In unicellular, colonial and filamentous forms
Buoyancy Regulation
Gas vesicles or gas vacuoles
Carbohydrate ballast
In planktonic forms
How are thylakoid membranes arranged and where are they
located in a cyanobacterial cell?
They are generally not stacked but are arranged concentrically at the periphery of the cell
What are phycobilisomes?
These house particular pigments that are linked by proteins
What are the 3 types of phycobiliproteins found in
cyanobacteria?
Phycocyanin: blue-green cyanobacteria
Phycoerythrin: red cyanobacteria
Allophycocyanin: (Red)
Why are cyanobacteria so successful at all PAR levels?
Cyanobacteria can alter their pigment composition in response to changes in light quality
Chromatic acclimation
What is the mode of reproduction in filamentous
cyanobacteria?
No sexual reproduction
Gene exchange by viral transduction
Filamentous cyanobacteria produce hormogonia which are single short filaments that serve as means of vegetative reproduction
What triggers and inhibits N2 fixation?
N2 Fixation is triggered by low NH4 and NO3
Requires large amounts of ATP
Requires Micronutrients (Mo, Fe, Mg, Co, V)
Inhibited by high O2
What is the name of the cells specialized for N2 fixation and
what is their role during this process?
Heterocytes
They reduce O2 toxicity effects on nitrogenase
Describe 2 adaptations or strategies that cyanobacteria
without specialized cells can use to fix N2.
Occurs under anaerobic conditions or at night
Down-regulation of photosystem II during N2 fixation (unicellular Cyanothece)
Division of labour (marine Trichodesmium)
Briefly explain the process of N2 fixation in cyanobacteria with
heterocytes.
Reduce O2 by thick mucilage walls, and bacteria at the surface
Absence of PSII
PSI exists to produce ATP
No C fixation
Carbohydrates imported from other cells
What are the similarities and differences between akinetes
and heterocytes?
Similarities:
Polysaccharides in cell walls
Inactivation of photosystem II
Differences:
akinetes have larger cells
No N2 fixation in akinetes
What morphological features are used to define
cyanobacterial taxonomy?
Thallus structure
Specialized reproductive cells
Heterocytes (presence/absence or location)
Akinetes
Mucilaginous sheath
Single or multiple filaments within a sheath
Hormogonia
Separation disks or necridia
Gas vesicles
