Introductory Microbiology Dr. Hala Al Daghistani

Introductory Microbiology Dr. Hala Al Daghistani

Why Study Microbes? Microbiology is the branch of biological sciences concerned with the study of the microbes. 1. Microbes and Man in Sickness and Health Parasitism; Pathogens (disease causing) Infectious disease is leading cause of death in developing countries (45%). Commensalisms; Natural Microbiota (do no harm) 2. Major Modern Applications (Biotechnology): Recombinant DNA technology; cloning Industrial Applications (antibiotics; chemical production via fermentation) Sewage treatment to decompose organic matter Bioremediation of toxic waste 3. The Role of Microbes in Ecosystems Sources for drug discovery (antibiotics & antiviral drugs) Cycling of Elements (ecosystem management; global climate change) Agriculture (crop diseases; nutrient enhancement)

Biotechnology & Bioremediation Biotechnology- when humans manipulate (micro)organisms to make products in an industrial setting Genetic engineering- create new products and genetically modified organisms (GMOs) Recombinant DNA technology- technology used to engineer GMOs capable of synthesizing desirable proteins (i.e. medicines, hormones, and enzymes) Bioremediation - activity of microbes in the environment helping to restore stability or clean up toxic pollutants Oil spills Chemical spills Water and sewage treatment

The microbial world is made up of microorganisms and viruses. Microorganisms are unicellular organisms (capable of existence as single cells), too small to be seen with the naked eye. Among all forms of life on the earth, microorganisms predominate in numbers of species and in biomass - because of their small size and the need for a microscope to see individual cells. (light microscope is generally required to visualize a single microbial cell) Viruses are noncellular entities and cannot be considered microorganisms. Viruses and cellular microorganisms are considered microbes. Viruses are not considered microorganisms because they are not cells. Viruses consist of nucleic acid (DNA or RNA) enclosed in a protein coat. They lack many essential properties of cells, including membranes, ribosomes and metabolic enzymes.

Which are the microorganisms? Life forms, or other self replicating entity, that requires microscopy technology to be clearly visualized. All prokaryotic and many eukaryotic life forms. Many are unicellular, sometimes cells are organized in filaments or clumps, and others are complex with only a portion of their life cycle being microscopic. Most can carry out life processes independently from other cells, others are highly parasitic. They often require specialized techniques for their study: microscopy, culturing, biochemical and molecular.

Biologists recognize the existence of two fundamentally different types of cells in the microbial world, called procaryotic and eucaryotic cells. 1. Eucaryotic cells have a "true" nucleus (the region of the cell that contains genetic information or DNA) that enclosed in a nuclear membrane 2. Procaryotic cells are said to have a "primitive" nucleus because their DNA is not enclosed within a nuclear membrane. The nuclear region of a procaryotic cell is sometimes referred to as a nucleoid, but never as a nucleus.

Note the difference in scale. The Eukaryotic cell would be about 50x bigger than the bacterium

Eukaryotic Cell Prokaryotic Cell Nucleus Present Number of chromosomes More than one Absent One--but not true chromosome: Plasmids Cell Type Usually multicellular Usually unicellular (some cyanobacteria may be multicellular) True Membrane bound Nucleus Present Example Animals and Plants Absent Bacteria and Archaea Genetic Recombination Meiosis and fusion of gametes Partial, undirectional transfers DNA Microtubules Present Endoplasmic reticulum Present Mitochondria Present Cytoskeleton Present Absent or rare Absent Absent May be absent DNA wrapping on proteins. Eukaryotes wrap their DNA around proteins called histones. Multiple proteins act together to fold and condense prokaryotic DNA.

Ribosomes Larger Vesicles Present Golgi apparatus Present Chloroplasts Flagella Permeability of Nuclear Membrane Plasma membrane with steroid Cell wall smaller Present Absent Present (in plants) Absent; chlorophyll scattered in the cytoplasm Microscopic in size; membrane bound; usually arranged as nine doublets surrounding two singlets Selective Yes Vacuoles Present Only in plant cells and fungi (chemically simpler) Submicroscopic in size, composed of only one fiber not present Usually no Usually chemically complexed Present Cell size 10-100um 1-10u

Procaryotic and Eucaryotic cells Eucaryotic cells are always bounded by a membrane, just as prokaryotic cells are. Some eucaryotic cells are also surrounded by a cell wall, but eucaryotic cells do not have capsules. Mitochondria are present in nearly all eucaryotic cells and produce the cell's energy by breaking down food. Chloroplasts, in contrast, are present only in plants and algae and are used in photosynthesis, the process through which the organism uses energy from the sun to build sugars.

Taxonomy of Life: The classification, or grouping, of organisms based on common characters used to reflect their evolutionary relatedness. Types of groups, taxa, are arranged in a hierarchy from the most general (Domain) to most specific. 3 Domains based on molecular analysis of ribosomal RNA. (Carl Woese 1980s) Two prokaryote domains: Bacteria and Archaea A single Eukaryote domain. Many Phyla within each domain.

Difference in taxonomy between us and them. Humans Domain: Eukarya Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Primata Family: Hominidae Group: Homo Species: sapiens Intestinal Bacterium Domain: Bacteria (no kingdom) Phylum: Proteobacteria Class: γ-proteobacteria Order: Enterobacteriales Family: Enterobacteriaceae Genus: Escherichia Species: coli Binomial nomenclature: Genus species (italic or underlined) Just like varieties, or races, there are strains of microbial species (e.g. Escherichia coli K12 versus the pathogenic E. coli O157:H7)

Viruses: An infectious particle with an acellular organization of protein and nucleic acids (RNA or DNA), and lacking independent metabolism. It requires the metabolism of a host cell in order to replicate. Viruses are about 50 to 200 nm in size. Prion: An infectious aberrant brain protein that causes abnormal aggregation of similar normal brain proteins; no nucleic acids. Causes dementia and madness.