Chapter 27 notes Genetic Reproduction 27 2 meiosis and fertilization do not occur in prokaryotes but transformation transduction and conjugation do when individuals are of diff species mvmnt of genes is horizontal gene transfer transformation geno and possibly pheno of prok cell are altered by uptake of foreign DNA from surroundings replaces own allele with foreign allele homologous DNA segments recombinant DNA in organism derived from two diff cells Once thought to be rare but found that many bacteria have cell surface proteins that recognize closely related DNA and transport it to the cell Foreign DNA can be incorporated into genome by homo DNA exchange Phages virus carry prok genes from one cell to other Results from accidents that occur during phage replicative cycle Virus itself cannot replicate so it attaches to another prok cell recipient and inject prok DNA acquired from first cell donor If some of this DNA is incorporated into recipient chromo by crossing over recombinant cell is formed Transduction Conjugation DNA transferred btwn two prok cells usually same species Temporarily joined In bacteria DNA transfer is always one way Pilus of donor cell attaches to recipient pilus retracts and pulls two cells together Mating bridge structure formed DNA transferred from donor to recipient Or DNA passes directly through hollow pilus Ability to form pili and donate DNA is from presence of piece of DNA called F factor f for fertility F factor Can exist as plasmid or segment of DNA within bacterial chromosome PLASMID Function as DNA donors if F Function as DNA recipients if F F converts F into F if a copy of entire F plasmid is transferred CHROMOSOME Chromosomal genes can be transferred during conjugation when donors cells F factor is integrated into chromo called an Hfr cell High Frequency for Recombination Like an F cell an Hfr cell functions as a donor during conj with F cell When chromo DNA from Hfr enters F Cell homo regions of Hfr and F chromos may align allowing DNA to be exchanged As a result recipient cell becomes recombinant bacterium with genes derived from the chromos of two diff cells new genetic variation R plasmids and antibiotic resistance Specific genes confer antibiotic resistance in pathogenic bacteria Sometimes mutation in a chromosomal gene of the pathogen can confer resistance a particular antibiotic into its cell reducing inhibitory effect Mutation in one gene may make it less likely that the pathogen will transport Mutation can also alter intracellular target protein for an antibiotic molecule Or bacteria can have resistance genes which code for enzymes that destroy or hinder effectiveness of certain antibiotics These resistance genes are often carried by plasmids known as R plasmids Exposing bacterial population to an antibiotic will kill antibiotic sensitive bacteria but not those that happen to have R plasmids with genes that counter the antibiotic According to NS antibiotic resistant bacteria population increases R plasmids like F plasmids have genes that encode pili and enable DNA transfer from one bac cell to other by conjugation 27 3 Extensive gen variation found in prokaryotes is reflected in their diverse nutritional adaptations Some are in common in euks but broad range of metabolic adaptations are in proks Organisms that obtain energy from light phototrophs Energy from chemicals chemotrophs Carbon source such as CO2 autotrophs Heterotrophs require at least one organic nutrient glucose to make other organic compounds Mode Autotroph Photoautotroph Chemoautotroph Light Inorganic chemicals H2S NH3 or Fe Energy Source Carbon Source Types of orgs CO2 HCO3 related CO2 HCO3 related PS proks cyano plants certain protists algae Unique to certain proks Sulfolobus Heterotroph Photoheterotroph Light Organic Unique to certain aquatic Chemoheterotroph Organic compounds compounds Organic compounds salt loving proks Rhodobacter Chloroflexus Many proks protists fungi animals some plants Prokaryote metabolism also varies with respect to Oxygen Obligate aerobes must use O2 for cell resp cannot grow without it Obligate anaerobes poisoned by O2 live exclusively by fermentation or extract chem energy by anaerobic respiration NO3 or SO4 2 Facultative anaerobes use O2 if present but can also carry out fermentation or anaerobic resp if in an anaerobic environment Nitrogen metabolism N is essential for all production of amino acids and nucleic acids in all organisms Euks can only obtain N from a limited group of N compounds Proks can metabolize N in many forms N fixation convert atm N to NH3 to incorporate fixed into amino acids and other organic molecules N fixing cyanobacteria are some of the most self sufficient organisms only need light CO2 N2 water and some minerals to grow N fixation has a large impact on other organisms N fixing proks can increase the N available in plants which cannot use atm N but can use the N compounds that proks produce from ammonia Metabolic Cooperation coop between prok cells allows them to use environmental resources that they could not use as individuals coop takes place btwn specialized cells of a filament Anabaena has genes that encode proteins for PS and for N fixation but a single cell cannot carry out both processes at the same time PS produces O2 which inactivates the enzymes involved in N fixation Most cells in a filament only carry out PS while a few specialized cells called Each heterocyst surrounded by thickened cell wall that restricts entry of O2 HETEROCYSTS carry out N fixation produced by neighboring PS cells cells and to receive carbs colonies known as BIOFILMS colonies to grow Intercellular connections allow heterocysts to transport fixed N to neighboring Metabolic cooperation btwn diff prok species often occurs in surface coating cells in a biofilm secrete signaling molecules that recruit nearby cells causing cells also produce polysaccharides and proteins that stick the cells to the substrate and to one another these polys and proteins that stick form the capsule or slime layer channels in the biofilm allow nutrients to reach cells in the interior and wastes to be expelled Example Sulfate consuming bacteria coexist with methane consuming archaea in ball shaped aggregates on ocean floor Bac appear to use the archaeas waste products such as org compounds and hydrogen In turn bacteria s produce sulfur compounds that the archaea use as oxidizing agents when they consume methane in the absence of oxygen These archaea consume