BIOL3711 Lecture Notes - Lecture 4: Monera, Asexual Reproduction, Anabaena
26 Jun 2018
School
Department
Course
Professor
Blue-green Algae
General
Photosynthetic, nitrogen fixation
Photosynthetic bacteria and general blue-green in colour
oAlso called, CYANOBACTERIA
Diversity
o7500 species
Nitrogen fixation
oSome species are capable of nitrogen fixation and significantly impact
the nitrogen cycle in the environment
Distribution
oOccurs singly or in colonies
oDiverse habitats as aquatic environments and also on land
Characteristics
Prokaryotes
oNo envelope is around the nuclear region
Cell wall
oConsists of polysaccharides and protein
oUsually gelatinous sheath extends beyond cell wall
Gas vacuoles
oFormed within the cell
oLook like dark and irregular particles under microscope
oFunction:
Adjust buoyancy and enable algae to control over their position
in the water column
Photosynthetic Pigments
Major:
oChlorophyll a
oB-carotene
Accessory:
oPhycocyanin – blue
oPhycoerythrin – red
Energy reserves
oCyanophycean starch
Appears as small granules
find more resources at oneclass.com
find more resources at oneclass.com
Thylakoids
oWhere photosynthesis happens
oFlattened sacs inside the chloroplast
Heterocysts
oLarge, walled cell: on FILAMENTS of
CYANOBACTERIA
oMorphology
Yellowish
Absence of granular reserve
material
Thick wall
Polar nodule
The thicker wall at both
ends of the heterocyst
The nodule connects the heterocyst with adjacent cells
oFunction
N2 NH
4 – N
Nitrogen fixation
Presence of nitrogenase inside the heterocyst
Anaerobic condition inside the heterocyst and
nitrogenase is VERY sensitive to oxygen
Nitrogen deficiency
oEspecially with low ammonia in environment
oMovement
Gliding and rotating around the longitudinal axis
Jerky movement
Reproduction
Asexual reproduction is the ONLY means of reproduction in blue-green algae
1. Vegetative
a. Formation of two cells by the separtuon of a parental cell
2. Endospores
a. Cells enlarge
b. Each protoplast divides up into a number of daughter cells WITHIN the
parent cell wall
3. Exospores
a. Spores are cut externally from a mother cell
4. Hormogonia
a. Fragments of a filament can become detached at the point of the
separation disc (SD) and glide away
b. The SD is the result of the death of a cell
5. Akinete
a. A cell with thickened wall, full of reserved nutrients
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Photosynthetic bacteria and general blue-green in colour: also called, cyanobacteria. Nitrogen fixation: some species are capable of nitrogen fixation and significantly impact the nitrogen cycle in the environment. Distribution: occurs singly or in colonies, diverse habitats as aquatic environments and also on land. Prokaryotes: no envelope is around the nuclear region. Cell wall: consists of polysaccharides and protein, usually gelatinous sheath extends beyond cell wall. Gas vacuoles: formed within the cell, look like dark and irregular particles under microscope, function: Adjust buoyancy and enable algae to control over their position in the water column. Accessory: phycocyanin blue, phycoerythrin red. Thylakoids: where photosynthesis happens, flattened sacs inside the chloroplast. Heterocysts: large, walled cell: on filaments of. The thicker wall at both ends of the heterocyst. The nodule connects the heterocyst with adjacent cells: function. Anaerobic condition inside the heterocyst and nitrogenase is very sensitive to oxygen. Nitrogen deficiency: especially with low ammonia in environment, movement.
