Chapter 27~ Prokaryotes and the Origins of Metabolic Diversity

Classification Domain: Bacteria –Found almost everywhere Domain: Archaea –Usually found in extreme environments

Structure of Bacteria Shape –cocci (sphere) Can be alone or in colonies –bacilli (rod) Usually solitary but can be in chains –helical (spiral) Corkscrew shape

Structural characteristics Almost all prokaryotes have a Cell wall –Made of peptidoglycan (sugars & proteins) Gram +: large amount of peptidoglycan outside of membrane Gram -: little peptidoglycan in between two membranes- outer one has lipopolysaccharides –Usually more harmful and resistant to drugs than gram + Capsule: adherence and additional protection Pili: adherence and conjugation

Motility Flagella Helical shape (spirochetes) SlimeTaxis –movement away or toward a stimulus

Form & Function Nucleoid region (genophore: non-eukaryotic chromosome) Plasmids Asexual reproduction: binary fission (not mitosis) “Sexual” reproduction (not meiosis): –transformation~ uptake of genes from surrounding environment –conjugation~ direct gene transfer from 1 prokaryote to another –transduction~ gene transfer by viruses Endospore: makes cell resistant in harsh conditions (250 million years)

Prokaryotic Growth Conditions for growth vary with species –cold conditions ( refrigerator) slow growth Most have generations times of 1-3 hours but some can divide every 20 minutes Statistic –1 cell could give rise to a colony weighing 1 million kg in 24 hrs if no limits on growth!!!!! Equals 2.2 million pounds in 24hrs!

Nutrition & Metabolism Photoautotrophs: photosynthetic; harness light to drive the synthesis of organic compounds (cyanobacteria) Chemoautotrophs: oxidation of inorganics for energy; get carbon from CO2 Photoheterotrophs: use light to generate ATP but get carbon in an organic form Chemoheterotrophs: consume organic molecules for both energy and carbon –saprobes- dead organic matter decomposers –parasites- absorb nutrients from living hosts

Nutrition & Metabolism Oxygen relationships: –Obligate aerobes Use O2 for cell. resp. and cannot live with out it –Facultative anaerobes Will use O2 if present but can grow by fermentation in anaerobic environments –Obligate anaerobes Poisoned by O2

Domain Archea Bacteria 3 main groups –Methanogens Give off methane, anerobes, live in swamps and marshes where O2 is low, give off methane gas –Halophiles Live in saline places like great salt lake –Extreme thermophiles Hot environments, deep sea vents

Domain Bacteria 5 Major groups ( see pg 514 of book)

Prokaryotic ecology Decomposers: unlock organics from corpses and waste products Symbiosis: –Symbionts ( organisms involed in relationship) / host –mutualism (+, +) Rhizobium and legumes –parasitism (+, -) Bacteria that cause illness –commensalism (+, 0) Bacteria in human body

Prokaryotes and Disease Opportunistic: normal residents of host; cause illness when defenses are weakened Ex. Streptococcues pneumoniae Exotoxins: bacterial proteins that can produce disease w/o the prokaryote present (botulism) Endotoxins: components of gram - membranes (Salmonella)