Microbiology Helmut Pospiech

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1 Microbiology Helmut Pospiech

2 The control of what gets in Passive transport along a concentration gradient often inefficient Active transport Requires energy consumption and what gets out

3 ABC (ATP binding cassette) More than 200 different ABC transporters known in prokaryotes Very high affinity of the binding protein to the substrate (< 1 µm) For the uptake of Sugars Amino acids Sulfate, phosphate Trace metals transporters

4 Strukture of ABC-transporters

5 Function of ABC-transporters, in this case ABC exporter

6 ABC-(ATP-Binding-Cassette)-transporter superfamily as ATP-driven membrane pumps Cystische Fibrose Transmembranaler Regulator

7 The cell wall of Eubacteria

8 The structure/composition of peptidoglycan lysozyme transpeptidase β lactam antibiotics (penicillins, cephalosporins)

9 The cell wall of gramnegative bacteria

10 The cell wall of grampositive bacteria

11 The cell wall of Mycobacteria Mycobacteria are pathogens that cause e.g. tubercolosis and leprae Slow growing Special cell wall structure haves evading immune system of the host

12 The impact of cell wall structure on taxonomy the Gram staining

13 Other cell surface structures of prokaryotes fimbriae and pili Fimbriae: Many per cell Used mainly for attachment Pili Only one or few per cell More extended than fimbriae Also used for attachment and intercellular communication

14 Other cell surface structures of prokaryotes capsules and slime layers Gel-like matrix around the cell Polymers often polysaccharides Sometimes amino acid polymers Evasion of immune system Biofilm formation (attachment) Increasing resistence against desiccation

15 Flagella Used for motility Bacteria differ in terms of number, size, position and function of flagella

16 The structure and function of a eubacterial flagellum

17 Flagella Biosynthesis

18 Chemotaxis moving relative to some concentration gradient of a chemical compound

19 How chemotaxis is achieved? Cell must have a memory system

20 Different ways to change direction while swimming

21 Gliding Motility Several mechanisms exist: Slime excretion cell pulled along by adherence Type IV pili Ratcheting movement

22 Secretion of proteins The sec system is the most common and important protein translocase in bacteria Structurally and functionally related to the secretion of proteins in the eukaryotic ER Depends on a signal sequence Also used for integral membrane proteins Mori & Ito (2001) Trends Microbiol. 9:

23 Several protein translocases are operational in bacteria Dependent on final destiny of the protein Desvaux et al. (2009) Trends Microbiol 17:139-45

24 Desvaux et al. (2009) Trends Microbiol 17:139-45

25 Desvaux et al. (2009) Trends Microbiol 17:139-45

26 Endospores Endospores are formed by certain bacteria as dormant (retsing) stage that is resistant to unfavourable environmental conditions like Heat Drying Acid Chemical disinfectants or radiation Nutrient exhaustion They can remain viable for extremely long periods of time Most endospore formers belong to the genera Bacillus and Clostridium Common Can be found in every soil sample

27 Structure of the endospore Very low water content Extremely little metabolic activity The core contains large amounts of small acid-soluble spore proteins (SASPs) Binds and protects DNA Serves as carbon source during germination) The core also contains large amounts of dipicolinic acid complexed with Ca 2+

28 Endospore formation Takes about 8 hours in B. subtilis 8 stages can be separated by microscope Is highly regulated More than 200 genes involved Transcription cascade

29 Endospores the ultimate survival package

30 Spore Germination Very rapid takes only few minutes 1. Activation Heat shock or prolonged rest phase 2. Germination Loss of dipicolinic acid SASP cleavage Water uptake 3. Outgrowth

31 How long can an endospore survive? Thermoactinomyces sp. from lake sediments and archaeological sites Several 1000 years Gest & Mandelstam 1987 Cano lab home page Bacillus sp. from insect guts embedded in amber? million years Cano & Borucki 1995 Halotolerant endospore former from primary salt crystals?? 250 million years Vreeland et al from Nature 407, 844