Cyanobacteria Reproduction Overview

Cyanobacteria Reproduction

• Fragmentation: Filamentous cyanobacteria break into smaller fragments called hormogonia which can grow into new filaments. This is a simple way for the organism to spread and colonize new areas.
• Hormogonia with Akinetes: Hormogonia are short filaments that can move and disperse. Akinetes are thick-walled dormant cells that form within the filament, acting as survival pods that can withstand harsh conditions and germinate into new filaments when conditions improve.
• Heterocyst – Akinete – Vegetative Cells (Anabaena sp.): Heterocysts are specialized cells that fix nitrogen. They are crucial for growth in nitrogen-poor environments. Akinetes are dormant cells that store nutrients and can withstand unfavorable conditions. Vegetative cells are responsible for photosynthesis and growth.
• Nannocytes (Aphanothece): Found in non-filamentous cyanobacteria like Microcystis, nannocytes repeatedly divide without enlarging within the parent cell. They germinate when conditions improve, giving rise to new colonies.

Cyanobacteria Ecology and Habitat

• Aquatic Habitats: Freshwater, marine, and estuarine/brackish water environments.
• Terrestrial Habitats: Soil crusts, rocks and moist surfaces, and polar regions
• Symbiotic Relationships: Cyanobacteria form symbiotic relationships with other organisms, such as in lichens.
• Ecological Importance: Cyanobacteria play crucial roles in nitrogen fixation, primary production, and biogeochemical cycles.
• Ecological Challenges: Harmful algal blooms (HABs) caused by some cyanobacteria can have negative impacts on water quality, aquatic life, and human health.

Cyanobacteria Common Examples

• Oscillatoria: A filamentous cyanobacteria that can form blooms in freshwater habitats.
• Microcystis: A colonial cyanobacterium found in freshwater environments.
  • Forms harmful algal blooms (HABs) in freshwater.
  • Produces microcystins, toxins harmful to aquatic organisms, livestock, and humans.

Rhodophyceae (Red Algae) - Reproduction

• Vegetative Reproduction: Occurs by fragmentation in most red algae.
• Asexual Reproduction: Gametophytes reproduce by neutral spores (monospores and polyspores) which develop in cells of the thallus.
  • Monospores develop in sporangia.
  • Polyspores are larger and more numerous.
  • Sporophytes reproduce by tetraspores, which form in tetrasporangia via meiosis.
  • Tetrasporangia produce tetraspores through meiosis (reduction division).
• Sexual Reproduction: Oogamous (oogamy).
  • Male structure: Spermatangia produce spermatia (male gametes).
  • Female structure: Procarp, containing a carpogonium (egg) and a trichogyne (receptive structure).
  • Egg development: Occurs within the basal swollen portion of the carpogonium.

Rhodophyceae (Red Algae) - General Information

• Economic Importance: Red algae are important for many economic applications.
  • Gelidium: A genus of thalloid red algae with over 124 species. Gelidium amansii is used in agar production.
  • Gracilaria: Economically important for agar production.
    • Used as a food source for humans, animals, and certain fish.
    • Plays a significant role in agar production.
• Habitat: Red algae are mostly found in the ocean, with a few freshwater species. They are commonly found growing attached to rocks or other algae, and are especially common in coral reefs and tidal pools.

Chlorophyta (Green Algae) - General Information

• Photosynthesis: Chlorophyta perform photosynthesis, converting sunlight into chemical energy stored as starch.
• Habitat: Approximately 90% of chlorophyta are found in freshwater environments, with 10% in marine environments.
• Structure: Chlorophyta exhibit a diverse range of structural forms.
  • Unicellular: Single-celled organisms, such as Chlamydomonas and Golenkinia.
  • Colonial: Groups of cells that live together in a colony without forming true multicellular structures, such as Volvox.
  • Filamentous: Algae that form long chains or filaments of cells, such as Spirogyra and Ulothrix.
  • Siphonous: Large, multinucleate cells without cross walls.

Chlorophyta (Green Algae) - Chloroplast

• Structure: The chloroplast contains chlorophyll, a pigment responsible for capturing light energy.
• Function: The primary function of the chloroplast is photosynthesis, the conversion of light energy into chemical energy. The chloroplast has several important structures:
  • Thylakoids: Membrane-bound compartments where light-dependent reactions occur.
  • Grana: Stacks of thylakoids that increase surface area for light absorption.
  • Stroma: The fluid surrounding the thylakoids where the Calvin cycle takes place.
• Pigments:
  • Lutein and Beta-carotene: Capture light energy and transfer it to photosystem reaction centers, protecting the photosynthetic apparatus from oxidative stress.
  • Zeaxanthin: Protects the photosynthetic apparatus from damage by dissipating excess light energy as heat.

This quiz covers the various reproductive methods of cyanobacteria, focusing on processes like fragmentation, hormogonia formation, and the roles of heterocysts and akinetes. Explore how these mechanisms enable cyanobacteria to thrive in diverse environments through reproduction and survival strategies.