Chapter 21: Prokaryotes and Viruses
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Chapter 21: Prokaryotes and Viruses 21.1 Characteristics of Prokaryotic Cells ☺ Prokaryotic Cells ☺ Smallest , most abundant and metabolically diverse ☺ Live in a variety of places ☺ No membrane bound nucleus ☺ Generally a single chromosome (a circular DNA molecule) ☺ Cell wall present in most species ☺ Reproduction mainly by prokaryotic fission Sizes and Shapes 1 and 10 micrometers in length three basic shapes 1. coccus – a spherical shape 2. bacillus – a rod shape 3. spirillum – a cell body with one or more twists Structural Features bacteria are prokaryotic cells a cell wall usually surrounds the plasma membrane the cell wall of eubacteria (prokaryotes) is composed of peptidoglycan molecules. Peptidoglycan - peptide groups crosslink numerous polysaccharide strands to one another bacterial species can be identified based of their cell wall structure and composition Gram Stain Technique Gram-positive (purple) have a thick peptidoglycan cell wall Gram-negative (pink) have a thin peptidoglycan cell wall Glycocalyx – a sticky mesh that encloses the cell wall and helps them to attach Bacterial flagella help bacteria to move Don’t have the 9+2 microtubule array as eukaryotic Flagella move by a corkscrew motion Many species have pili – short protein projections that help cells adhere to surfaces Metabolic Diversity Bacteria are the most abundant and inhabit diverse places Photoautotrophic bacteria build organic compounds by photosynthesis “selffeeders” They tap sunlight for energy and use carbon dioxide as their carbon source. Chemoautotrophic bacteria are self-feeders. Carbon dioxide is the usual carbon source Photoheterotrophic bacteria are not self-feeders. They use energy from the sun for photosynthesis, but their carbon sources are fatty acids, complex carbohydrates and other compounds. Chemoheterotrophic bacteria are parasites or saprobes not self-feeders. Parasites live on or in a living host and draw nutrients from it. Saprobic - get nutrients from the organic products, wastes or remains of other organisms. 21.2 Prokaryotic Growth and Reproduction The Nature of Growth We measure bacterial growth as an increase in the number of cells in a given population Each cell divides into two How fast they divide depends on type Prokaryotic Fission A bacterium cell divides into two daughter cells Each cell inherits a single bacterial chromosome Bacterial chromosome – a circularized, double-stranded DNA molecule that has only a few proteins attached to it. Prokaryotic Fission – a parent cell replicates its DNA Two molecules of DNA attach to plasma membrane New membrane grows between the two attachment sites Deposits of new membrane and new wall material extend down into cytoplasm Cell divides into two. A. bacterial chromosome is attached to plasma membrane F. Cell divides the cell in two B. DNA replication starts. proceeds in 2 directions C. new copy of DNA is attached at membrane near the attachment site of parent DNA E. deposits of new membrane and new cell wall extends down into cytoplasm D. new membrane grows between attachment sites Conjugation Between Cells daughter bacterial cells may also inherit one or more plasmids Plasmid – a small self-replicating circle of extra DNA that has a few genes The F (fertility) plasmid has certain genes that confer the means to engage in bacterial conjugation. Bacterial Conjugation A donor cell transfers plasmid DNA to a recipient cell A conjugation tube forms between two DNA replication starts and DNA moves through tube Cells separate This is common in Salmonella, Streptococcus and E. Coli. A. conjugation tube formed between a donor and a recipient cell. Enzyme nicked donors plasmid B. DNA replication starts on nicked plasmid. DNA strand moves through tube D. cell separates from each other. Plasmids Circularize C. in recipient cell, replication starts on transferred DNA 21.3 Classifying Prokaryotes Numerical Taxonomy – traits of a unidentified cell are compared with those of a known bacterial group Cell shape, motility, staining, nutritional requirements, metabolic patterns The greater the total number of traits that the cell has in common with the known group, the closer is the relatedness. Comparing rRNA is useful and uniting some groups that did not even appear to be related on the basis of other tests. Domain Bacteria Domain Archae – ancestors of eukaryotic cells 21.4 Domain Bacteria Representative Diversity ☺ The most ancient lineage of prokaryotic cells ☺ Include: ☺ Photoautorophs ☺ Chemoautotrophs that cycle nutrients in habitats ☺ Chemoheterotrophs – most diverse, many species are dangerous parasites and pathogens ☺ Cyanobacteria ☺ Blue-green algae ☺ They released oxygen during photosynthesis ☺ Some are symbionts with fungi in lichens ☺ Specialists in nitrogen fixation ☺ Proteobacteria ☺ Most diverse monophyletic group of bacteria ☺ All gram-negative ☺ Important in nutrient cyclers 21.5 Archaeans The Third Domain ☺ Are prokaryotic but are similar to eikaryotes ☺ Make histones ☺ They make the same start codon ☺ Their RNA polymerases and some transcription factors are more eukaryotic than prokaryoticthe domain has been subdivided into three major groups ☺ Euryarchaeota ☺ Crenarchaeota ☺ Korarchaeota 3 major groups 1. Methanogens (Euryarchaeota) Make methane Live in swamps, stockyards, termite and mammalian gut and other oxygenfree habitats Produce ATP by anaerobic Produce 2 billion tons of methane every year. 2. Extreme Halophiles (Euryarchaeota) Salt lovers Spoil commercial sea salt, salted fish, and animal hides Make ATP by aerobic Found Great Salt Lake, Dead Sea, and seawater evaporation ponds 3. Extreme Thermophiles (Crenarchaeotes) Geothermal heated soils, sulfur-rich hot springs, volcanic vents Heat lovers Do best at above 80c Are anaerobes 21.6 The Viruses Virus means poison Virus – a noncellular infectious agent that has two characteristics 1. consists of a protein coat wrapped around a nucleic acid core 2. the virus cannot reproduce itself (can only reproduce after it enters a host cell) genetic material of a virus is DNA and RNA the coat of a virus consists of one or more types of proteins the coat protects the genetic material during the journey to a host cell. Coats of complex viruses have sheaths tail fibers and other structures attached The vertebrate immune system detects certain viral proteins, but genes in viruses mutate at such a fast rate they often elude the immune fighters. Examples of Viruses Each kind of virus can multiply only in certain hosts Bacteriophages – a group of viruses that infect bacterial cells Animal viruses Virus contains double or single-stranded DNA or RNA Size range from 18 nanometers to 350 nm Many cause diseases such as the common cold, cancers, warts, herpes, HIV Plant viruses must enter plant cell wall to cause disease so they hitch a ride on sucking devices of insects. DNA Viruses Parvovirus – causes fever and rash in small children, aggravates sickle-cell anemia symptoms Adenovirus – causes respiratory infections RNA Viruses Retroviruses – include HTLV-1, HTLV-2, and HIV Coronaviruses – upper respiratory infections colds. 21.7 Viral Multiplication Cycles 5 basic steps of viral multiplication 1. Attachment Virus attaches to host 2. Penetration Either the whole virus or its genetic material alone penetrates the cells cytoplasm 3. Replication and Synthesis The viral DNA and RNA directs the host cell into producing many copies of viral nucleic acids, proteins, and enzymes 4. Assembly Viral nucleic acids and proteins are put together to form new infectious particles 5. Release New virus particles are released from the cell Lytic and lysogenic pathways are common replication cycles for bacteriophages Lytic pathway proceeds rapidly new particles are released when a host cell undergoes lysis Lysis – the plasma membrane, cell wall or both are damaged so the cytoplasm leaks out and the cell dies Lysogenic pathway – extends the lytic cycle The virus does not kill its host, instead a viral enzyme cuts a host chromosome then integrates viral genes into it When an infected cell prepares to divide it replicates the recombinant molecule Provirus – during this cycle, the virus is temporarily in a dormant state Prophage – same as provirus but with bacteriophage Environmental factors trigger virus and it again becomes active 5. lysis of host cell Lytic Cycle 4. Tail fibers are added 1. virus binds to host cell viral genetic material enters 3. viral proteins are assembled into coats and DNA is packed inside 2. viral DNA tells host to produce viral proteins and copies of viral DNA Lysogenic Cycle 1A. viral DNA becomes integrated in bacterial chromosome 4A. viral DNA is excised from chromosome 2A. prior to prokaryotic fission chromosomes and viral DNA 3A. after binary fission each daughter cell will have is replicated recombinant DNA Chapter 21: Prokaryotes and Viruses 21.1 Characteristics of Prokaryotic Cells Prokaryotic Cells _______________, most abundant and metabolically _______________ No membrane bound _______________ Generally a single chromosome (a circular DNA molecule) Reproduction mainly by prokaryotic fission Sizes and Shapes 1 and 10 micrometers in length three basic shapes 1. coccus – 2. bacillus – 3. spirillum – Structural Features Bacteria are _______________ cells A cell wall usually surrounds the plasma membrane The cell wall of eubacteria (prokaryotes) is composed of peptidoglycan molecules. Peptidoglycan – Bacterial species can be identified based of their cell wall structure and composition Gram Stain Technique Gram-positive Gram-negative Glycocalyx – Bacterial flagella help bacteria to move Many species have pili – Metabolic Diversity Bacteria are the most abundant and inhabit diverse places ____________________ bacteria build organic compounds by photosynthesis “selffeeders” They tap sunlight for energy and use carbon dioxide as their carbon source. Chemoautotrophic bacteria are ____________________. Carbon dioxide is the usual carbon source ____________________ bacteria are not self-feeders. They use energy from the sun for photosynthesis, but their carbon sources are fatty acids, complex carbohydrates and other compounds. Chemoheterotrophic bacteria are parasites or saprobes, not self-feeders. Parasites live on or in a living host and draw nutrients from it. Saprobic – 21.2 Prokaryotic Growth and Reproduction The Nature of Bacterial Growth We measure bacterial growth as an increase in the number of cells in a given population Each cell divides into ________ How fast they divide depends on type Prokaryotic Fission A bacterium cell divides into two daughter cells Each cell inherits a _______________ bacterial chromosome Bacterial chromosome – Prokaryotic Fission – Two molecules of DNA attach to plasma membrane New membrane grows between the two attachment sites Deposits of new membrane and new wall material extend down into cytoplasm Cell divides into two B. bacterial chromosome is attached to plasma membrane F. Cell divides the cell in two B. DNA replication starts. proceeds in 2 directions C. new copy of DNA is attached at membrane near the attachment site of parent DNA E. deposits of new membrane and new cell wall extends down into cytoplasm D. new membrane grows between attachment sites Conjugation Between Cells Daughter bacterial cells may also inherit one or more plasmids Plasmid – The F (fertility) plasmid has certain genes that confer the means to engage in bacterial conjugation. Bacterial Conjugation A donor cell transfers plasmid DNA to a recipient cell A conjugation tube forms between two DNA replication starts and DNA moves through tube Cells separate This is common in Salmonella, Streptococcus and E. Coli. A. conjugation tube formed between a donor and a recipient cell. Enzyme nicked donors plasmid B. DNA replication starts on nicked plasmid. DNA strand moves through tube D. cell separates from each other. Plasmids Circularize C. in recipient cell, replication starts on transferred DNA 21.3 Classifying Prokaryotes Numerical Taxonomy – The greater the total number of traits that the cell has in common with the known group, the closer is the relatedness. Comparing _______ is useful and uniting some groups that did not even appear to be related on the basis of other tests. Domain Bacteria – Domain Archae – 21.4 Domain Bacteria Representative Diversity ☺ The most ancient lineage of prokaryotic cells ☺ Include: ☺ ☺ _______________ that cycle nutrients in habitats ☺ Chemoheterotrophs – ☺ Cyanobacteria ☺ ☺ They released __________ during photosynthesis ☺ Some are _______________ with fungi in lichens ☺ Specialists in nitrogen fixation ☺ Proteobacteria ☺ Most diverse monophyletic group of bacteria ☺ ☺ Important as nutrient cyclers 21.5 Archaeans The Third Domain Are prokaryotic but are similar to eukaryotes They make the same ____________ ____________ Their RNA polymerases and some transcription factors are more eukaryotic than prokaryotic The domain has been subdivided into three major groups 3 major groups 1. Methanogens (Euryarchaeota) Live in swamps, stockyards, termite and mammalian gut and other oxygenfree habitats 2. Extreme Halophiles (Eu Spoil commercial sea salt, salted fish, and animal hides Found Great Salt Lake, Dead Sea, and seawater evaporation ponds 3. Extreme Thermophiles Geothermal heated soils, sulfur-rich hot springs, volcanic vents Do best at above _____C 21.6 The Viruses Virus means ________________ Virus – 1. 2. Genetic material of a virus is _______ and _______ The coat of a virus consists of one or more types of _______________ The coat protects the genetic material during the journey to a host cell. Coats of complex viruses have sheaths, tail fibers, and other structures attached The vertebrate immune system detects certain viral proteins, but genes in viruses mutate at such a fast rate they often elude the immune fighters. Examples of Viruses Each kind of virus can multiply only in certain hosts Bacteriophages – Animal viruses Size range from _____ nanometers to ______ nm Many cause diseases such as the common cold, cancers, warts, herpes, HIV Plant viruses must enter plant cell wall to cause disease so they hitch a ride on sucking devices of insects. DNA Viruses Parvovirus – Adenovirus – RNA Viruses Retroviruses – Coronaviruses – 21.7 Viral Multiplication Cycles 5 basic steps of viral multiplication 1. Attachment 2. Penetration 3. Replication and Synthesis The viral DNA and RNA directs the host cell into producing many copies of viral __________ _______, ____________, and ____________ 4. Assembly Viral nucleic acids and proteins are put together to form new infectious particles 5. Release Lytic and lysogenic pathways are common replication cycles for bacteriophages Lytic pathway New particles are released when a host cell undergoes lysis Lysis – Lysogenic pathway The virus does not kill its host, instead a viral enzyme cuts a host chromosome then integrates viral genes into it When an infected cell prepares to divide it replicates the recombinant molecule Provirus – Prophage – Environmental factors trigger virus and it again becomes active 5. lysis of host cell Lytic Cycle 4. Tail fibers are added 1. virus binds to host cell viral genetic material enters 3. viral proteins are assembled into coats and DNA is packed inside 2. viral DNA tells host to produce viral proteins and copies of viral DNA Lysogenic Cycle 1A. viral DNA becomes integrated in bacterial chromosome 4A. viral DNA is excised from chromosome 2A. prior to prokaryotic fission chromosomes and viral DNA is replicated 3A. after binary fission each daughter cell will have recombinant DNA
