BIOB 170 N 1st Edition Lecture 2 Introduction Prokaryotes Prokaryotes are the earliest of life forms that appeared around 3.5 billion years ago.Their phylogenetics is unclear particularly at the phylum and class levels. Standardphylogenetics concepts may not apply to prokaryotes because of “horizontal gene flow.” Domain: Archaea Archaea were initially thought to be the most archaic of prokaryotes. They exhibit features of both bacteria and eukaryotes. General Characteristics Archaea are generally considered thermophiles (90-113oC) and halophiles. Habitats that include these organisms are hot springs with very low pH. However, they can be found in many other extreme environments. Many are methanogens found in anaerobic aquatic sediments. There are three distinctive Archaean traits. They lack peptidoglycan in the cell wall. Some have histones. Others are not sensitive to antibiotics. Domain: Bacteria Bacteria are the most widespread forms of life on earth. They fit in numerous ecological niches and have great metabolic diversity. Distinguishing features Many bacteria have a flagella, cell walls/extra-cellular features, genome organization, reproduction, and metabolic diversity. - Bacterial flagella are fundamentally different from eukaryotes. Eukaryotic flagella (undulipodium) consist of distinctive protein microtubule array (axoneme).These flagella are membrane-bound and rooted to the cytoplasm. These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Bacterial flagella consist of stiff tubular protein (filament). These flagella are not membrane-bound. Supports intelligent design. Bacterial metabolic diversity Autotrophic organisms make organic compounds (food). Examples of this are cyanophytes and purple-sulfur bacteria. There are two types of autotrophy – photosynthetic and chemosynthetic. - Photosynthetic organisms use light sources to make energy. It can be oxygenic ornon-oxygenic. Examples of organisms that use oxygenic photosynthesis are the cyanobacteria. Examples of organisms that use non-oxygenic photosynthesis are purple-sulfur bacteria. - Chemosynthetic organisms use organic or inorganic resources to make energy. Chemical energy is released by oxidation of the compounds. Oxidation is the removal of electrons and H from molecules to release energy. It yields energy to drive glucose formation. Heterotrophic organisms require pre-made organic compounds. There are two types of heterotrophy – photoheterotrophic and