EBIO 3400 1st Edition Lecture 14Outline of Last Lecture I. Type of FungiOutline of Current Lecture II. Genetics (bacterial)III. The Mosaic Nature of GenomesIV. Horizontal gene transfer- TransformationV. Horizontal gene transfer – Conjugation VI. PlasmidsVII. DNA Transfers between Bacteria and EukaryaVIII. Gene Transfer by Phage TransductionCurrent LectureI. Bacterial genetics- Bacteria can pass on genetic traits both vertically and horizontallyA. Vertical = passing the trait from generation to generation during binary fission and production of spores (clonal growth) or copying the DNA in a spore) - Traits being passed down generation to generation B. Horizontal = passing the trait from cell to cell of the same generationTransductionTransformationConjugation-Gene transfer results in a genotypic (e.g. genes for pilus) and phenotypic (e.g. pilus) change in the recipient cellThis is also how dangerous traits like antibiotic resistance can spread through bacterial populations without reproduction (binary fission) having to occurThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.C. Once inside the cell DNA needs to incorporate into the chromosome or a plasmid via:Recombination orTransposition II. The Mosaic Nature of Genomes- A surprise arising from bioinformatic studies is the mosaic nature of all microbial genomes.a. Example: Escherichia coli’sgenome is rife with genomic islands, inversions, deletions etc.- This is the result of horizontal gene transfer, recombinations, and a variety of mutagenic and DNA repair strategiesIII. Horizontal gene transfer- Transformation1. Transformation… uptake and incorporation (into the chromosome or a plasmid) of“naked” DNA from the environment…. Expression of this new DNA can alter the phenotype of the organism, e.g. converting a non-pathogen into a pathogen…. e.g. Streptococcus pneumoniaecapsule genes- It was discovered by Frederick Griffith in 1928- The transforming principle, DNA, was identified in 1944 Transformation provided the first clue that gene exchange can occur in Bacteria. Genome comparisons show that the fundamental purpose of bacterial gene transfer is to acquire genes that might be useful as the environment changesWhat was known about S. pneumoniae when transformation was discovered?S = smooth colony due to capsuleR = rough colony due to no capsuleExperiment carried out by Griffin, showing that something was transferred from dead, pathogenic, S. pneumoniae to live nonpathogenic cells - transforming them into pathogens withcapsules (this process can also occur in vitro aka in test tube*It was later (1944) shown that the “transforming principle” was DNA (thus studies of transformation led to identification of DNA as the genetic material in cells). Mechanism of transformation  Many cells are capable of natural transformation. - The cells need to be competent. Others require artificial manipulations.- Perturbing the membrane by chemical (CaCl2) or electrical (electroporation) methods Why do species undergo natural transformation?- Use indiscriminate DNA as food- Use specific DNA to repair damaged genomes- Acquire new genes through horizontal gene transfer Gram-positive bacteria transform DNA usingQuorum Sensing --transformasomecomplex. CF = competencefator Gram-negative bacteria transform DNA without the use of competence factors (CF). Either they are always competent, or they become competent when starved.Note:Transformation can take place between even unrelated bacteria (but it is rarer than between related because most foreign DNA is degraded before it can be integrated into the chromosomeIV. Horizontal gene transfer – Conjugation - Conjugation (bacterial “sex”) Usually occurs between a + strain (+ a conjugative plasmid) and a - strain (no plasmid)- Conjugation is the transfer of DNA from one bacterium to another, following cell-to-cell contact= bacterial sex - It is typically initiated by a special pilus protruding from the donor cellV. PlasmidsA. Review: Extrachromosomal DNA  Plasmids are much smaller than chromosomes. - Found in archaea, bacteria, and eukaryotic microbes- Usually circular- Need host proteins to replicate  Plasmids are advantageous under certain conditions:- Resistance to antibiotics and toxic metals- Pathogenesis- Symbiosis Plasmids can also be transferred between cells. Plasmids have tricks to ensure their inheritance:- Low-copy-number plasmids segregate equally to daughter cells.High-copy-number plasmids segregate randomly to daughter cellsAll sorts of traits can be transferred via conjugative plasmids - the most relevant traits for us are antibiotic resistance genes…. But other important genes are also found on plasmidsAntibiotic resistance (R-factors) - usually by coding for an enzyme that renders the antibiotic non-functional. Beta-lactamase (inactivates Beta-lactams) is one example. Penicillin is a Beta-lactam.Special metabolic properties - some plasmids allow bacteria to take advantage of situations that might be otherwise harmful. Breakdown of complex organic molecules is often plasmid encodedVirulence Plasmids - there are a number of ways that a plasmid can confer virulence in a bacterium. 1) The production toxins toward the host or towards other bacteria (bacteriocins andantibiotics). 2) The ability to form a capsule. Virulent B. anthracis have 2 plasmids that encode for toxin production and capsule formation. Other virulence factors on plasmids: The production ofsiderophores(e.g. S. aureus).Adhesins - capsules or fimbriae that allow the bacterium to adhere to specific cells* The real scary thing about plasmids is that many of them have the above traits AND are conjugative Conjugation is brought about via information on fertility plasmids (= conjugative plasmids)… which contain genes for:1. The F pilus2. Genes to mobilize the plasmid (Transfer factors)3. Origins of replication Conjugation requires the presence of special transferable plasmids1. These usually contain all the genes needed for pilus formation and DNA export A well-studied example in Escherichia coli is the fertility factor (F factor).2. Contains two replication origins:1. oriV: used in nonconjugating cells2. oriT: used during DNA transfer Conjugation begins with contact between the donor cell, called the F+ cell, and a recipient