Bacteria The yellow band surrounding this hot spring is sulfur, a waste product of extremophilic prokaryotes, probably of the Domain Archaea, Kingdom Archaebacteria. Bacteria are prokaryotic cells (no nucleus). Prokaryotic cells are about 10x smaller than eukaryotic cells. There are more prokaryotes on Earth than all other organisms combined! All prokaryotes were once classified in the Kingdom Monera. Today, the two prokaryotic Domains are Archaea and Bacteria, and the two Kingdoms are Archaebacteria and Eubacteria. Prokaryotes were first! They set up and run the global life system we all live within! 9
Classifying Prokaryotes: Eubacteria Plasma Membrane Peptidoglycan Cell Wall The protein-charbohydrate compound making up the Eubacteria cell wall. Capsule Polysaccharide Some (Pathogens!) Protective & Sticky Outer Membrane Phospholipid Some Protective & Selective Only Gram - Support & Protection Flagellum Locomotion Selective Barrier DNA Nucleoid (no envelope) Pili Ribosomes Protein Translation Plasmid (DNA) Antibiotic resistance & conjugation Cytoplasm Aqueous solution (cytosol) for metabolism + organelles Attachment & conjugation This diagram represents D. Bacteria, K. Eubacteria, and species Escherichia coli. Review and add the functions of each structure labeled in the diagram. In general, Eubacteria are more diverse and occupy more habitats than Archaebacteria. 10
Classifying Prokaryotes: Archaebacteria Archaebacteria generally look like Eubacteria in their outward appearance. We can tell them apart by their ultrastructure. Archaea cell walls have S-layer proteins, no peptidoglycan. Archaea plasma membranes have different lipids. Archaea genes have exons & introns, Bacteria similar to D. Eukarya, suggesting Cyanobacteria common ancestry. They have these differences to survive harsh environments (extremophiles). Methanogens live in anaerobic environments, like mud, and produce methane. Halophiles are salt-loving and live in hypersaline environments. Thermophiles are heat-loving, some living in boiling water! Eukarya Archaea 11
Identifying Prokaryotes: Eubacteria A microscope is needed to see individual prokaryotes? It is impossible to identify different species visually. Microbiologists use primarily differences in cell wall structure and metabolism to identify different species or strains? Looking at living Eubacteria using a light microscope can help distinguish shape and locomotion. Their nutrient supply can be altered and their waste products detected in cell culture to distinguish them (metabolism). Gram staining determines the ultrastructure of the cell wall. Gram bacteria have an outer Gram membrane, Gram + don t. Staining This information would be useful to doctors attempting to cure a bacterial infection because many antibiotics act on the cell wall and affect Gram + vs. Gram bacteria differently. The most effective means of distinguishing bacterial species or strains is through their metabolism. Bacilli Cocci Spirilli 12
Identifying Prokaryotes: Metabolic Diversity Mycobacterium tuberculosis Cyanobacteria Deep Oceanic Vent Tube Worm Bacteria Chemoheterotroph Photoautotroph Chemoautotroph The two general requirements to sustain life are energy and matter (primarily carbon). Metabolism refers to all the chemical reactions in a cell or organism necessary to process energy and matter. The two matter handling modes of prokaryote metabolism are heterotrophic ( other feeding, like us) and autotrophic ( self feeding, like plants). The two energy handling modes of prokaryote metabolism are cellular respiration (chemical energy from food) and photosynthesis (making food with light). Chemoheterotrophs (animals) get both carbon and energy from organic food. Photoheterotrophs (bacteria only!) get carbon from food and energy from light. Photoautotrophs (plants) get carbon from inorganic CO 2 and energy from light. Chemoautotrophs (bacteria only!) get carbon from inorganic CO 2 and energy from inorganic chemicals, like hydrogen sulfide (H 2 S). Prokaryote metabolic diversity is highly variable because they have been here longest! The two processes prokaryotes utilize to break down food molecules and convert energy for cellular work are aerobic cellular respiration and fermentation. 13
Identifying Prokaryotes: Metabolic Diversity Aerobic cellular respiration is the catabolic process of using oxygen to get energy from food molecules. Aerobic means with oxygen or using oxygen. Anaerobic fermentation is the catabolic process of getting energy from food without using oxygen. Anaerobic means without oxygen, or not using oxygen. Obligate means one has no choice or option, has to. Facultative means capable of but not restricted to a particular function or mode, does not have to. This demonstration suggests that these are different species or strains of bacteria because their metabolic response to oxygen is different. The bacteria in culture 1 are obligate aerobes that must have oxygen to survive. The bacteria in culture 2 are obligate anaerobes that must stay away from oxygen to survive. The bacteria in culture 3 are facultative anaerobes that can survive both with and without oxygen, but survive better with oxygen because aerobic cellular respiration is more efficient than anaerobic fermentation. Air-medium interface Bacterial cells Culture Medium Bacteria in liquid cultures. Test tube [O 2 ] [O 2 ] 14