BIOLOGY OF BACTERIA LAST DAY Brief introduction to

BIOLOGY OF BACTERIA

LAST DAY • Brief introduction to bacteria, Archaebacteria, and bacterial culturing media.

TODAY • We will start by looking at our cultures, and providing colony descriptors. • We will learn about the Biology of Bacteria • Bacteria structure • Bacterial shapes • We will look at microscopes again to observe bacterial shapes under the microscope

BIOLOGY OF BACTERIA • Part 1: Bacterial Cell structure • Table 24 -2 in your text book. • Bacteria typically are composed of a cell wall, cell membrane, and a cytoplasm. • Some bacteria have distinctive structures that serve as a protective layer (endospores, capsules, outermembranes)

BACTERIAL CELL WALL • Both Archaebacteria and Eubacteria have cell walls • Eubacterial cell walls are made of a molecule known as PEPTIDOGLYCAN • Peptidoglycan is a polymer consisting of sugars and amino acids, which forms a mesh like barrier outside the bacterial plasma membrane • Gram Negative bacteria have an outer membrane protects peptidoglycan, meaning some antibiotics are ineffective against GN bacteria.

CELL MEMBRANE AND CYTOPLASM • In Bacteria, cell membrane carries out cellular respiration (metabolism of bacteria; producing energy) in absence of mitochondria (like in eukaryotes) • Unlike Eukaryotes, bacteria DO NOT CONTAIN MEMBRANE BOUND ORGANELLES (i. e. no nucles, no golgi apparati, no mitochondria) • Cytoplasm consists mainly of Ribosomes and DNA • Bacterial DNA is arranged in a single closed loop • Aside from the main chromosome, Bacteria also have plasmids, which are self replicating loops of DNA

CAPSULE AND PILI • Many bacterial species produce an outer covering called a capsule • Protects cell from drying, harsh chemicals and immune cells • Glycocalyx: • Fuzzy, sticky capsule around bacteria which allows it to attach to host cell and tissue • Pili • Short protein projections on surface of bacteria, which aid in attachment/adherence to host cells

ENDOSPORE • Dormant structure produced by some Gram Positive bacteria • Thick outer covering that surrounds bacterial DNA • Not reproductive cells, they allow bacteria to survive harsh environmental conditions • When conditions become favourable, the living bacteria will emerge and continue multiplying • Formed by the genera Bacillus and Clostridium

BACTERIAL MOVEMENT • Typically propelled by a flagella • Protein structures, which turn and propel the bacteria in an erratic “run and tumble” motion • Bacteria can have a single flagellum, a tuft of flagella at one end, flagella at both ends, or flagella completely surrounding the cell • Some bacteria can mobilize by sliding on a slime layer they produce (myxobacteria) or move in a corkscrew like motion (spirilla)

INTRO TO BACTERIAL SHAPES AND CLASSIFICATION • Most bacteria have three basic shapes: • Bacilli (rod shaped) • Cocci (spherical/circular) • Spirilla (corkscrew shaped)

BACILLI • Rod shaped bacterium

COCCI • Circular/spherical shaped bacteria • Streptococci (chains) Staphylococci (clusters) Diplococci (dual)

SPIRILLA • Corkscrew shaped

GRAM POSITIVE V GRAM NEGATIVE • Bacteria are typically classified as either Gram Positive or Gram Negative based on their color following the Gram staining procedure

GRAM POSITIVE BACTERIA • Appear purple under the microscope following a Gram stain • Crystal Violet stains the Peptidoglycan on GP cell wall • Remember Pur. Ple = Positive Staphylococcus aureus

GRAM NEGATIVE BACTERIA • Appear pink following Gram stain under microscope • GN cells are protected by an outer membrane which prevents the peptidoglycan from being stained. • The counterstain Saffranin gives GN cells the pink colour • Remember pi. Nk= Negative Escherichia coli

TO DO NOW • Observe some of the different bacterial shapes around the classroom • Draw them on a blank sheet of paper • Make sure to label whether they are cocci, bacilli or spirilla, and Gram + or Gram -