Lecture 1 Meet the Microbes 2024 PDF

Meet the Microbes Lecture topics Lecturers Meet the Microbes Dr Merve Suzan The Microbial Planet Zeden A history of human-microbe Prof Vince interactions O’Flaherty Medical Microbiology Prof Gerard Wall Prokaryotic genetics Dr Kate...

Meet the Microbes Lecture topics Lecturers Meet the Microbes Dr Merve Suzan The Microbial Planet Zeden A history of human-microbe Prof Vince interactions O’Flaherty Medical Microbiology Prof Gerard Wall Prokaryotic genetics Dr Kate Microbial molecular Reddington diagnostics A. Prof Florence Microbiomes Abram Environmental Microbiology Dr Gavin Collins Microbes & Food Production Dr Alma Siggins Food Preservation Methods Dr Katrina Lacey Marine Microbiology Tutorials/Practicals To understand what bacteria are we first need to consider the basic unit of life – THE CELL A cornerstone of Science Basic units of matter are atoms Basic units of compounds are molecules Basic units of life are cells. Cells are not simply building blocks of life. Cells themselves are what is alive in the organism.  CELLS Cells are the most highly organized assemblages of dissimilar molecules on Earth - probably in the Universe! All living organisms are composed of cells. The cell is basic unit of life and biological structure and function. Unicellular organisms: single celled organisms e.g. bacteria, algae, protozoa etc. Multicellular organisms: more than one cell, cells are subunits of tissues and organs e.g. plants, animals etc.  CELL THEORY Cells are basic units of life. No organism has been found that shows attributes of life that is not composed of cells. All organisms are constructed of cells: either unicellular or multicellular. Cells arise from pre-existing cells: never by aggregation of cell parts or cell chemicals.  CELLS Cells comprise the parts of all living things. They make possible the life functions of: Organization Movement Energy use Reproduction Response to stimuli Growth  CELL TYPES Compare biochemical activities of cells from diverse sources: amazing similarities. All have heritable characteristics coded by DNA. All use same mechanisms for formation and storage of energy. All have identical methods of protein, polysaccharide and nucleic acid synthesis. Morphologically there are very major variations. These different morphological types can be resolved into cells of two types. These differ fundamentally in their internal organization: Prokaryotes = bacteria and archaea Eukaryotes = algae, yeast, fungi, protozoa, plants, animals etc.  Membrane-bound nucleus EUKARYOTIC CELL which contains DNA, organized into chromosomes. Eukaryoticcells contain several types of membrane- enclosed internal structures called organelles. Some are equivalent in function to unbounded regions in prokaryotic cells, others have functions unique to eukaryotes. Eukaryotes = algae, yeast, fungi, Eukaryotes have network of protozoa, plants, animals etc. minute filaments and tubules: Unicellular and multicellular cytoskeleton, which gives shape and allows movement PROKARYOTIC CELL No nucleus DNA is localized into a region but is not enclosed within a membrane-bound nucleous. Do not contain membrane- bound organelles. All prokaryotes are independent, single celled organisms and include Prokaryotes = bacteria and archaea. thousands of species of Unicellular bacteria and archaea.  VIRUS Virus consist of 2 or 3 components only Genetic material DNA or RNA A protein coat (capsid) to protect the genetic material Sometimes a lipid envelope surrounding the protein coat That’s it!  A virus can only replicate inside a host where they use the hosts machinery and metabolism – not theirs VIRUS Viruses have an extracellular form that is metabolically inert Viruses infect all forms of cellular life including bacteria, fungi, plants, insects, animals etc.  Microorganisms Viruses Prokaryotes Eukaryotes Bacteria Algae Archaea Fungi Protists Fungi Algae Saccharomyces Agaricus Protists Unicellular Diatoms cerevusuae bisporus Unicellular amoeba  SIZE MATTERS Bacteria typically range in size from 1 – 10 μm Virus 20 to 250 nm 1 m = 100 cm (centimeters) 1 cm = 10 mm (millimeters) 1 mm = 1000 μm (micrometers) 1 μm = 1000 nm (nanometers)  Morphology of Prokaryotes Variety of sizes and shapes.  Range in size from 1-10 µm.  Most eukaryotic cells are about 10 times bigger than medium sized bacteria.  Size difference because eukaryotic cells must accommodate nucleus, mitochondria and organelles.  Morphology of Prokaryotes Prokaryoteshave no nucleus or organelles, DNA and enzyme clusters etc can fit in a smaller volume. Large majority of prokaryotes are single-celled. However, some form clusters  BACTERIAL SHAPE A variety of different shapes are found. spherical (cocci) rod shaped (bacilli) spiral (spirilla) Shape is used in identification of bacteria Cocci (spheres) in pairs (Diplococci) Cocci in chains (Streptococci) Cocci in irregular clusters (Staphylococci) Straight rods (Bacilli) Curved rods (Vibrio-like)  BACTERIAL CELL STRUCTURE Common feature = cell wall. Gives shape, support and protection to plasma membrane and cytoplasm. Composed of huge carbohydrate and protein chains: peptidoglycan polymers or murein. Some bacteria have cell wall made up of only a single thick layer of peptidoglycans outside the plasma membrane. Some bacteria have an additional protective coating - the capsule.  BACTERIAL CELL WALL Gram- Gram- positive negative BACTERIAL CELL CYTOPLASM Extensive compartmentalization of cytoplasm by membranes is not found in bacteria. Cell cytoplasm in which is (nucleoid) dissolved various enzymes, RNA sugars amino acids etc. Lack cytoskeleton - so cannot actively move plasma membrane or cell surface. Plasma membrane provides a surface to which organelles can attach and carry out such processes as secretion, DNA replication etc.  Prokaryotic genome Have about 1/1000 DNA of a Eukaryote No nucleus. DNA is present as tangled mass in nucleoid region of cell - less dense than surrounding cytoplasm. DNA is arranged into a bacterial chromosome. Chromosome consists of a single, circular ring of DNA. In addition to the one major chromosome, bacteria may have plasmids.  PLASMIDS Small circular rings of DNA Not part of the chromosomal DNA Each plasmid consists of just a few genes. In most environments, bacteria can survive without their plasmids. All essential functions being encoded on the chromosome. Plasmids carry genes for things like antibiotic resistance, metabolism of unusual substrates etc. Plasmids replicate independently of main chromosome and can be transferred between cells.  BACTERIAL CELL MOVEMENT Some bacteria cannot actively move and require wind, water or other organisms to move them. Many move toward light, food etc. and away from chemicals, toxins and waste (taxis). Movement is often by a flagellum. Bacterial flagella look and function completely differently from eukaryotic flagella.  SUMMARY Prokaryote and Eukaryote cells Prokaryotes = bacteria and archaea Eukaryotes = everything else e.g. algae, protists, fungi, plants and animals Viruses have genetic material, a protective coat and can only replicate inside a hosts’ cell  SUMMARY 2 Bacterial morphology – rods, cocci, spiral Movement by a flagellum Prokaryote cells Cell wall Plasma membrane Cytoplasm Genetic information on a chromosome Plasmids