Lecture 16 Archaea and Phototrophs Flashcards
Describe the major groups of archaea.
Archaea include three major groups: Euryarchaeota, Crenarchaeota, and Korarchaeota. They exhibit diverse metabolic capabilities and inhabit various environments.
Explain the significance of Lokiarchaeota in relation to Eukaryotes.
Lokiarchaeota, an archaeal phylum, shares genetic similarities with eukaryotes. Its discovery suggests a potential link between archaea and the origins of eukaryotic cells.
How were methanogens historically recognized (by who?), and what characterized the establishment of archaea as a distinct domain of life?
Methanogens, recognized by Volta in the 1770s, were later classified as archaea in the late 1970s. This classification established archaea as a distinct domain with diverse characteristics and environments.
Define the superphyla within archaea and why do they present challenges in study?
TACK, DPANN, and Asgard are archaeal superphyla. They present challenges in study due to limited cultivated members and the need for shotgun metagenomic sequencing.
Highlight the diversity within the Euryarchaeota phylum
Euryarchaeota, the most diverse archaeal phylum, includes methanogens, halophiles, acidophiles, and thermophiles.
Describe the discovery of the Asgard superphylum, focusing on Lokiarchaeota, and its potential role in the evolution of eukaryotes.
Asgard, including Lokiarchaeota, was discovered in the deep sea. The isolated member, Prometheoarchaeum syntrophicum, shares similarities with eukaryotes, supporting the hypothesis of eukaryotic evolution from archaea.
List and describe the different groups of phototrophic microbes, emphasizing their metabolic flexibility.
Phototrophic bacteria are distributed across seven phyla, primarily exhibiting anoxygenic photosynthesis. Cyanobacteria, capable of oxygenic photosynthesis, are an exception.
Provide an overview of green sulfur bacteria, including their habitat preferences, anaerobic nature, and photosynthetic mechanisms
Green sulfur bacteria are obligate anaerobes found in anoxic, sulfide-rich zones in lakes. They utilize chlorosomes for photosynthesis and fix CO2 via the reductive TCA cycle. (yellow stone national park)
Discuss the characteristics of green non-sulfur bacteria
including their filamentous, gliding motility and habitat preferences.
Green non-sulfur bacteria are filamentous and exhibit gliding motility. They possess varied metabolic capabilities and inhabit neutral to alkaline hot springs.
Introduce purple non-sulfur bacteria found in the phylum Proteobacteria, describing their photosynthetic apparatus and habitat requirements.
Purple non-sulfur bacteria thrive in organic-rich, low-sulfide environments. They possess intracytoplasmic membranes for photosynthesis.
Highlight the unique capabilities of Cyanobacteria
Cyanobacteria exhibit diverse morphology, including unicellular and filamentous forms. They differentiate into akinetes, heterocysts, and hormogonia, showcasing their unique capabilities. also capable of oxygenic photosynthesis
what are heterocysts used for?
Nitrogen fixation. They thicken cell walls and create an environment that can synthesize nitrogenase. (anaerobic)
Purpose/features of Akinetes?
resistant, dormant cells that allow cyanobacteria to survive adverse environmental conditions (unfavourable temperatures,etc) formation is a strategy…
Purpose/features of hormogenia?
small filaments, disperse easily, fragmentation. Allow cyanobacteria to disperse easily and colonize new areas and favourable environments.
Define chromatic adaptation in phototrophs
Chromatic adaptation enables phototrophs to optimize photosynthesis by adjusting the relative amounts of light-harvesting pigments.
