Microbiology Prokaryotic Genetics PDF

2425-BO101 Biology – Prokaryotic Genetics Dr Kate Reddington: [email protected] [email protected] Lecture 1 / 2 E-mail: [email protected]. Location: Microbiology Room 103 Universit Contact hours: Tuesday 3pm-4pm (...

2425-BO101 Biology – Prokaryotic Genetics Dr Kate Reddington: [email protected] [email protected] Lecture 1 / 2 E-mail: [email protected]. Location: Microbiology Room 103 Universit Contact hours: Tuesday 3pm-4pm (Email in advance) y ofGalway. 1 ie  Learning Objectives LO1 Explain the structure and function of biomolecules LO2 Describe the form and function of cells LO3 Discuss organism diversity and evolutionary mechanisms LO4 Relate basic principles of organismal interactions LO5 Critically evaluate major human impacts on the environment LO6 Understand the role of biological sciences in societal development Universit y Universit ofGalway. y ie ofGalway. 2 ie  Tree of Life by Domain *Viruses cannot be included in the tree of life because they do not share Universit characteristics with cells, and no single gene is shared by all y viruses or viral lineages Universit ofGalway. y ie ofGalway. 3 ie  Cell Biology Cell biology has been studied since 16th century Cells are small units of living material that make up all living things Humans have billions of cells in their bodies, while a single bacterium is made up of one cell Cell biology is the field of science that studies cells to understand how they work Universit y Universit ofGalway. y ie ofGalway. 4 ie  Cell Biology Cells are the fundamental unit of living organisms (the building blocks) The invention of the telescope made the Cosmos accessible to human observation - the microscope opened up smaller worlds. Introduction- Traditional Methods 5 6 Classifying Microbes Introduction- Tradtional Methods 7  Cell Biology - Similarities Prokaryotes/Bacteria Eukaryotes Introduction- Plasma membrane (phospholipid bilayer and regulates permeability) Traditional Methods Genetic material – DNA Cell Wall – except animal cells Ribosome - catalyse protein synthesis Cytoplasm/cytosol – comprising of water, glucose, proteins and ions. 8 https://www.youtube.com/watch?v=URUJD5NEXC8 9  Prokaryotes/Bacteria Eukaryotes Plants, animals, fungi and protists Bacteria (algae and protozoa) Size: 1-10mm Size: 10-100mm Cell Wall Cell Wall – only plants, fungi and protists No distinct subcellular (cellulose) organelles Well defined subcellular compartments Circular chromosome – nucleoid bounded by lipid membranes Often plasmids, RNA and Cytoplasm consists of organelles, ribosomes, Ribosomes cytoskeleton (shape, movement and Unicellular or multicellular organises many metabolic functions) Escherichia Coli (E. Coli) is most Cytoskeleton: microtubules made of tublin & studied bacterium microfilaments made of actin. Most are multicellular 10 Differentiate to specialized tissue/cells  Prokaryotes/Bacteria Cell membrane (plasma membrane or bacterial cytoplasmic membrane): a permeability barrier for most molecules and serves as the location for the transport of molecules into the cell Cell wall: bacterial cell wall provides structural integrity to the cell, a protective structure that allows them to survive Capsule: The capsule found in some species enables the microorganism to attach to surfaces, protect microorganisms from dehydration and attack by phagocytic cells, and makes pathogens more resistant to our immune responses. Pili: (singular, pilus) used for attachment to surfaces Flagella: (singular, flagellum) used for locomotion Nucleoid Region: refers to the region of the cytoplasm where chromosomal DNA is located Chromosome: consists of double–stranded circular DNA Ribosome: site for protein synthesis 11  “Earth could contain nearly 1 trillion microbial species, with only one-thousandth of 1 percent now identified, a new study suggests” Altogether, these data represent more than 5.6 million microscopic and nonmicroscopic species from 35,000 locations from all the world’s oceans and continents, except Antarctica 12  Prokaryotic diversity – Vertical Gene Transfer There are hundreds of thousands of bacterial species in existence on Earth They grow relatively quickly, and most reproduce by binary fission, the production of two identical daughter cells from one mother cell Each replication cycle doubles the number of cells in a bacterial population The bacterial chromosome is a long circle of deoxyribonucleic acid (DNA) that is attached to the membrane of the cell. During replication, the chromosome is copied, and the two copies are divided into the two daughter cells. 13  Prokaryotic diversity – Horizontal Gene Transfer Mutations that develop in one bacterial cell can also be passed to related bacteria of different lineages through the process of horizontal transmission Horizontal gene transfer, also known as lateral gene transfer, is a process in which an organism transfers genetic material to another organism that is not its offspring There are three main forms of horizontal transmission used to spread genes between members of the same or different species: conjugation, transduction and 14 transformation  Prokaryotic diversity – Horizontal Gene Transfer The ability of Bacteria and Archaea to adapt to new environments as a part of bacterial evolution most frequently results from the acquisition of new genes through horizontal gene transfer It is estimated that as much as 20% of the genome of Escherichia coli originated from horizontal gene transfer! Horizontal gene transfer is able to cause rather large-scale changes in a bacterial genome For example, certain bacteria contain multiple virulence genes called pathogenicity islands that are located on large, unstable regions of the bacterial genome These pathogenicity islands can be transmitted to other bacteria by horizontal gene transfer However, if these transferred genes provide no selective advantage to the bacteria that acquire them, they are usually 15 lost by deletion Horizontal Gene Transfer- Conjugation Bacterial conjugation refers to the transfer of DNA between bacterial cells that requires cell-to-cell contact The steps of bacterial conjugation are: mating pair formation, conjugal DNA synthesis, DNA transfer, and maturation 16  Horizontal Gene Transfer- Transformation Transformation is a form of genetic recombination in which a DNA fragment from a dead, degraded bacterium enters a competent recipient bacterium and is exchanged for a piece of DNA of the recipient. Some bacteria, such as Neisseria gonorrhoeae, Neisseria meningitidis, Hemophilus influenzae, Legionella pneomophila, Streptococcus pneumoniae, and Helicobacter pylori tend to be naturally competent and transformable During transformation, DNA fragments are released from a dead degraded bacterium and bind to DNA binding proteins on the surface of a competent living recipient bacterium. 17 Horizontal Gene Transfer- Transduction Bacterial transduction is a type of gene transfer where a bacterium transfers its DNA (or a portion of it) to another bacterium (that is not its offspring) by using a virus as a vector Unlike other processes of gene transfer like horizontal gene transfer and conjugation, transduction does not require the physical contact between the host cell and the cell that will donate the DNA. 18  Which molecule has consistently been used today relating to the above words? 19  Bacterial Genomes The living process of all cells are governed by their complement of genes (known as the genome) In cells a gene can generally be defined as a segment of DNA that encodes a protein In prokaryotic cells DNA is present a in large double stranded molecule called the bacterial chromosome In most prokaryotes, DNA is circular and a single chromosome is present Prokaryotes are usually haploid microorganisms as they contain a single copy of most genes 20  E. coli Genome E. coli – a typical bacteria has a singular circular chromosome of 4.68 million base pairs of DNA It contains ~4300 genes A single cell of E. coli contains ~1900 kinds of protein- some are very abundant, others are not E. coli has mechanisms for controlling expression of genes- not all are active at all times 21 DNA 22  Deoxyribonucleic Acid (DNA) is the blueprint for life It contains all the necessary information to make a new organism 23  DNA Structure  DNA consists of two molecules that are arranged into a ladder- like structure called a Double Helix.  A molecule of DNA is made up of millions of tiny subunits called nucleotides.  Each nucleotide consists of: 1. Phosphate group 2. Pentose sugar 3. Nitrogenous base  DNA Structure Four kinds of nitrogenous bases: Purine bases A = Adenine G = Guanine Pyrimidine bases T = Thymine C = Cytosine 25  DNA Structure Because of this complementary base pairing, the order of the bases in one strand determines the order of the bases in the other strand 26  Why Study DNA All living organisms contain DNA. This amazing macromolecule encodes all of the information needed to program the cell's activities including reproduction, metabolism and other specialized functions By studying the DNA and genomes of bacteria we are able to better understand their metabolic capabilities, their ability to cause disease and also their capacity to survive in extreme environments 27 Why study Prokaryotic genetics? 28