Presentation on theme: "Prokaryotes (the fancy way to say Bacteria)"— Presentation transcript:
1 Prokaryotes (the fancy way to say Bacteria) Chapter 27
2 OutlinePrevalence of ProkaryotesProkaryotic DiversityProkaryotic ComplexityProkaryotic VariationProkaryotic MetabolismHuman Bacterial DiseasesBenefits of Prokaryotes
3 Prevalence of Prokaryotes In almost every place or environment microbiologists (scientists who study small organisms) look, prokaryotes have been found.Hot springs, hypersaline environments, highly toxic gaseous environment, within clean rooms of hospitalsIn the 1980’s a new method of classification was usedDivided prokaryotes into 2 groups:Archaebacteria (Archae) and bacteria
4 Prevalence of Prokaryotes Prokaryotes are the oldest, structurally simplest, and most abundant forms of life on earth.abundant for over 2 billion years before the appearance of eukaryotesProkaryotic synthesis (from cyanobacteria) is thought to have been the source for much of the earth’s oxygen in atmosphere5,000 different kinds currently recognized
6 Structure of a Prokaryotic Cell Most prokaryotic cells are small and lack interior organization.The plasma membrane is enclosed within a rigid cell wallDNA not contained within a membrane-bounded nucleus.Prokaryotes exteriorly may have a flagellum and other outgrowths called pili.Pili aid in attachment to other cells
7 Prevalence of Prokaryotes Prokaryotic formbacillus (bacilli) straight and rod-shapedcoccus (cocci) spherical shapedspirillum (spirilla) long and helical shapedSome bacillus and coccus bacteria form coloniesSpirilla generally do not form colonies and are often free swimmingSome bacterial colonies form spore producing structures.
8 Prevalence of Prokaryotes Prokaryotic formCoccusDiplococcuspairsStreptococcuschainsTetradquads
10 Prevalence of Prokaryotes BacillusSingleStreptococcobacillus (no pics)
11 Prevalence of Prokaryotes Spiral TypesVibrioComma shapedSprilliumThick rigid spiralSpirocheteThin flexible
12 Prevalence of Prokaryotes Prokaryotes versus Eukaryotesunicellularitysome may form filamentous matricescell size1 μm or less in diameterMay vary by 5 orders of magnitudechromosomes“naked” (no protein) circular DNA located in nucleoidcell division and recombinationbinary fission (asexual)internal compartmentalizationNo internal compartments (mitochondria or chloroplasts)only organelle is the ribosomeflagellaSingle protein flagella of flagellinSpin like propellers instead of whiplikemetabolic diversitySeveral kinds of anaerobic and aerobic photosynthesisChemoautotrophs
13 Prokaryotic Diversity Original key classification characteristicsphotosynthetic or nonphotosyntheticmotile or nonmotileunicellular or colony-forming or filamentousspore formation by division or transverse binary fission
14 Prokaryotic Diversity Now prokaryotic classification completed with genetic and molecular approachesAnalysis of amino acids sequence of key proteinsNucleic acid analysis by establishing % guanine (G) and cytosine (C)nucleic acid hybridizationribosomal RNA sequencingwhole genome sequencing
15 Kinds of ProkaryotesVery early, prokaryotes split into two linesArchaea and bacteria are as different in structure and metabolism from each other as either is from eukarya.Archae (archebacteria) not actually as old as Bacteria
16 Prokaryotic Diversity Comparing archaebacteria and bacteriaplasma membranescomposed of different lipidscell wallarchaebacteria lack peptidoglycangene translation machineryBacteria ribosomal proteins and RNA polymerases different from eukaryotesarchaebacteria similar to eukaryotesgene architecturebacteria genome not interrupted by intronssome archaebacteria posses introns
17 Prokaryotic Complexity Prokaryotic cell surface – identifying featurescell wall maintains shape and protects the cell from swelling and rupturingusually consist of peptidoglycanGram-positive - thicker peptidoglycan(purple color after stain)Gram-negative - thinner peptidoglycan(red color after stain)flagella – slender protein - locomotionpili - hairlike structures – attachment (7.5 – 10 nm)endospores - resistant to environment
20 The Cell Interior Internal membranes invaginated plasma membrane for respiration and/or photosynthesisNucleoid regionlack nucleus - genes encoded with single double-stranded DNA*Prokaryotes often posses plasmids: independently replicating circle of DNA that contain only a few genes (not usually essential for survival)RibosomesProkaryotic ribosomes are smaller than eukaryotic ribosomes, and differ in protein and RNA content.Some antibiotics (tetracycline and chloramphenicol) bind to prokaryotic ribosomes to block protein synthesis
21 The Cell Interior Internal membranes (a) aerobic bacterium exhibits extensive respiratory membranes within cytoplasm(b) cyanobacterium has thylakoid-like membranes that provide sites for photosynthesisDo you think that it is likely that photosynthetic and respiratory membranes evolved more than once?How could your idea be tested experimentally?
22 Processes to Create Prokaryotic Variation mutationspontaneous errors in DNA replicationprokaryotic ability to mutate rapidly often has adverse effect on humansRadiation, UV light, and various chemicals (mutagens) cause DNA replication errorsNormal mutation rate 1 per million basesE. coli has 5000 genesThis means that 1 out of every 200 bacteria will have a mutation1 spoonful of soil has 1 billion bacteria, so there should be 5 million mutant individuals per spoonful!
23 Processes to create Prokaryotic Variation mutationwith sufficient nutrients, a typical bacterium population could double in 20 minutes.this allows for mutations to spread rapidlyindividual bacterium not killed by an antibiotic can then reproduce rapidly and after 30 generations (10 hours) there would be over 1 billion clones of this resistive bacteriaSome hospitals now have strains of Staphyloccus aureus that are penicillin resistantWhy then could antibiotic soaps be a problem?Why should you take all 10 days of your medication?
24 Processes to create Prokaryotic Variation mutation –figure 27.7
25 Processes to create Prokaryotic Variation genetic recombinationoccurs by gene transfer from one cell to another by viruses or conjugationconjugation: temporary union of 2 unicellular organisms, during which genetic material is transferred from one cell to another.this is another method that can lead to resistant bacteria
26 Prokaryotic Metabolism Autotrophsobtain carbon from inorganic CO2photoautotrophs – use sunlight to build organic molecules from CO2chlorophyll a as pigment and H20 as electron donorbacteriochlorophyll as pigment and H2S as electron donorchemoautotrophs - inorganic chemicalsobtain energy by oxidizing inorganic substancesNitrifiers – oxidize ammonia or nitriteOn ocean floors H2S is oxidized as it escapes from thermal vents
27 Prokaryotic Metabolism Heterotrophsobtain carbon from organic moleculesphotoheterotrophs – sunlight + organic Cpurple non-sulfur bacteriaorganic molecules such as carbohydrates or alcohols source for Cchemoheterotrophs (most prokaryotes)carbon and energy from organic moleculesmost decomposers and pathogens
28 Prokaryotic Metabolism How heterotrophs infect host organismsproteins secreted by type III systemmay be used to transfer other virulence proteins into nearby eukaryotic cells
29 Human Bacterial Diseases Tuberculosisafflicts respiratory system and easily transmitted from person to person through the airDental cariestooth decay caused by bacteria present in plaquehigh sugar diets increase tooth decaylactic acid bacteria ferment sugars and reduce pH, thus degenerating tooth enamel