Microbiology I: Prokaryote Classification and Genetics Notes PDF

Biology Applications Microbiology I: Classification and Structure of Prokaryotic Cells  Lecture Objectives Know the difference between prokaryotic and eukaryotic cell structure List and recognize the common shapes of bacteria Compare and contrast the cell walls of typical gram- positive...

Biology Applications Microbiology I: Classification and Structure of Prokaryotic Cells  Lecture Objectives Know the difference between prokaryotic and eukaryotic cell structure List and recognize the common shapes of bacteria Compare and contrast the cell walls of typical gram- positive and gram-negative bacteria The Human Body is Home to Diverse Microbiomes Some Bacteria That Cause Illness in Humans Phylogeny of some major lineages of Bacteria and Archaea A Comparison of the Three Domains of Life  Identifying Bacteria Morphology (shape, structure, aggregation, staining) Cell Wall Composition Movement Mode of Metabolism Atmospheric requirements Prokaryotes: Review Most prokaryotic cells are very small 0.5-5μm Variety of shapes Spherical (Cocci) Rod-shaped (Bacilli) Spiral (Spirilla) (a) Spherical (b) Rod-shaped (c) Spiral Cocci Bacilli Spirilla Bacterial Shapes and Arrangements Relative size of different biological targets of interest  Prokaryotic characteristics: Review Lack nuclear membrane Generally single, circular chromosome in a nucleoid Lack membrane- bound organelles Compartment in cytoplasm Lack spindles and asters Internal components: -_____________ -_____________ -________________ -_____________ -_____________ Prokaryotic characteristics: Review Lack eukaryotic organelles Golgi apparatus, endoplasmic reticulum, mitochondria, chloroplasts Single compartment within cell membrane Lack spindles and asters Have components outside of the cell wall -capsules and slime layers -fimbriae and pili Bacterial cell wall Peptidoglycan Maintain cell shape Hypertonic Protect inside of ell Prevents cell bursting Hypertonic environment Hypotonic Cell shrivels Hypotonic environment Cell bursts Isotonic Isotonic environment Peptidoglycan Gram staining Used to classify bacteria based on cell wall composition Gram-positive bacteria Simpler walls with large amount of peptidoglycan Gram-negative bacteria Less peptidoglycan, outer membrane can be toxic  Flagellar Propulsion Flagella are used to move in aqueous environments Bacterial mechanism Rotor at the base of flagella Powered by proton/chemical gradient  Flagellar Arrangement Atrichous – no flagella Monotrichous - single flagellum Amphitrichous a flagellum at each end Lophotrichous - clusters of flagella at the poles of the cell Peritrichous - flagella distributed over the entire surface of the cell. Elgamoudi 2014  Genetic Variation through Gene Transfer Lateral gene transfer allows for acquisition of traits not otherwise available via ____________ Transformation—when bacteria or archaea naturally take up DNA from environment released by cell lysis or secreted Transduction—viruses pick up DNA from one prokaryotic cell and transfer it to another cell Conjugation—genetic information transferred by direct cell-to-cell contact—includes event called _______________  Reproduction Prokaryotes reproduce by binary fission Can divide every 1-3 hours Key features They are small Short generation times Considerable genetic variation Binary Fission Reproduction Factors adding to genetic diversity Rapid reproduction Mutation Genetic recombination Prokaryotes are highly evolved! Evolution can occur quickly  Conjugation One way DNA transfer Genetic material transferred between prokaryotic cells Sex pilus Donor cell attached to recipient by pilus Piece of DNA called F factor required for production of pili Conjugation Bacterial F plasmid chromosome F+ cell F+ cell (donor) Mating bridge F− cell (recipient) Bacterial F+ cell chromosome (a) Conjugation and transfer of an F plasmid Hfr cell (donor) A+ A+ A+ A+ A− A+ F factor A− A− A+ A− Recombinant F− cell F− bacterium (recipient) (b) Conjugation and transfer of part of an Hfr bacterial chromosome, resulting in recombination R plasmids R plasmids carry genes for antibiotic resistance Specific R plasmids lead to antibiotic resistance Natural selection Allows for increase in resistance in population exposed to antibiotics Increase in antibiotic resistant bacteria Transformation Transfer of DNA from dead cells DNA fragment exit cell Free-floating DNA picked up by other cells DNA incorporated via recombination Transduction Phage DNA 1 Phage infects bacterial donor cell with A+ and B+ A+ B+ alleles. Movement of genes between Donor cell bacteria by 2 Phage DNA is replicated and proteins synthesized. A+ B+ ____________ 3 Fragment of DNA with A+ allele is packaged within a phage capsid. A+ Crossing over 4 Phage with A+ allele infects bacterial recipient cell. A+ A− B− Recombinant Recipient cell 5 Incorporation of phage DNA cell creates recombinant cell with genotype A+ B−. A+ B− Summary Prokaryotes can be divided into two lineages, Bacteria and the Archaea, based on a variety of morphological, biochemical and molecular characters. Bacteria and Archaea are very small, prokaryotic cells, and most are unicellular There are three basic shapes of bacteria: coccus, bacillus, and spiral. Based on planes of division, the coccus shape can appear in several distinct arrangements: diplococcus, streptococcus, tetrad, sarcina, and staphylococcus. Prokaryotes reproduce asexually by binary fission. Genetic variation in prokaryotes can be achieved through transformation (uptake of DNA from the environment), transduction (transfer of DNA from one cell to another by a virus), and conjugation ( direct transfer of DNA from one cell to another).