Lecture 1b Bacterial Cell Structure Next inner most part of bacterial cell Cell Wall Protects the cell from osmotic shock a lot of water can kill you It will swell up the cell and blow up Composed of peptidoglycan unique to bacteria not found in humans plants and fungi and is a good anitbiotics peptido peptide protein glycan glucose carbohydrate Peptidoglycan NAM NAG NAM NAG Composed of long chains of alternating NAM NAG NAM NAG N acetylmuramic acid NAM and N acetylglucosamine NAG Attached to each NAM is a tetrapeptide NAM L Alanine D Glutamic Acid Diaminopimelic Acid D Alanine note Diaminopimelic Acid is a derivative of the amino acid Lysine and is found nowhere else in nature except in the bacterial cell wall also D amino acids are not used to make proteins why Nutrasweet has no calories Cross Linked Petidoglycan Adjacent Glycan chains can be cross linked to each other in two different ways 1 A peptide inter bridge between the Diaminopimelic Acid of one glycan chain and the D Alanine of another the composition of this inter bridge varies between species Gram 2 The tetrapeptides are joined directly Gram Peptidoglycan http sp uconn edu terry images other peptidoglycan gif gram inter bridge Cross Linking imagine Rubber cement GRAM weak soluble Rubber Car tire gram and lasts longer strong tough insoluble Gram and Gram The cell wall of some bacteria respond differently to a particular staining procedure called the Gram Not surprisingly this behavior is the result of structural differences between these bacteria Gram Cell Wall Thick peptidoglycan layer 30 layers peptide inter bridge Teichoic Acids project outward from peptidoglycan layer immunogenic Lipoteichoic Acids project inward from peptidoglycan layer to cytoplasmic membrane anchor Fully permeable Gram Cell Wall Resistance to certain antibotic Thin peptidoglycan layer no peptide inter bridge Outer Membrane unique structure bilayer of phospholipid inner lipopolysaccharide outer Porins span the outer membrane size exclusion protects from some antibiotics Lipopolysaccharide LPS Immunegetic Heat stable Endotoxin composed of elicits all the symptoms of a bacterial infection different types of LPS species ID Periplasm just underneath the outer membrane houses secreted degradative enzymes pathology Stored temporarily in periplasm Penicillin the first broad spectrum antibiotic Disrupts cross linking between glycan molecules Makes pepto layer weak More effective against Gram because Penicillin is excluded by porins in Gram also resistance due to the evolution of penicillinase Unusual Cell Walls TB Mycobacterium largely composed of mycolic acid making them appear waxy and more resistant to chemicals dehydration antibiotics pathology Propels water and anything in water more resistant to ecoli Bacteria w o a Cell Wall Mycoplasmas lack a cell wall altogether pleomorphic penicillin resistant Cell Membrane underneath cell wall regulates transport into out of the cell 50 phospholipid 50 integral membrane proteins Embedded in membrane Phospholipid http bioweb wku edu pix cells P lipid2 gif Long hydrocarbon chains Non polar region Phospholipid bilayer http www rcscsd org apbio notes membranes htm If you mix them up with water it spontaneously form all membrane Phospholipid Bilayer Water can go in and out Freely permeable to water dissolved gases and small hydrophobic molecules by Can go into out of cell simple diffusion high concentration low concentration Hydoplic molecules are too big to go through cells glucose amino acids How do bacteria aquire most of their raw materials Transport Proteins Symporters transport of two substances in the same direction i e sugars Antiporters transport of two substances in opposite directions i e Na H H antimicrobials anitbiotics Uniporters transports one substance in one direction either in or out i e cations potassium calcium Group Translocation clever especially for bacteria The substance is chemically altered during transport phosphotransferase system i e glucose and other sugars The cell can soak up all the glucose by converting into glucose phosphate How do bacteria sense and respond to their environment Receptors transduce chemical signals from outside the cell to inside the cell Cell Membrane http www rdc ab ca scottpsych website student 475chp1 htm Receptor protein Bacterial Chromosome Allows a larger bacterial cell A single circular supercoiled double stranded DNA molecule 1 mm long the cell is 1 m long 1 1000X one per cell replicates only when the cell divides 1000 5 000 Kbp relatively small compared to human chromosomes Bacterial Chromosome single where one gene goes so do all the others little variation circular easier to replicate than linear humans have linear dsDNA like ours replicates like ours 1 5kb genetically simple few genes easier to understand Bacterial Chromosome http www bact wisc edu themicrobialworld structure html extra chromosomal DNA Plasmids very small 2 10 Kbp autonomously replicating Even when cell doesn t replicate circular double stranded DNA molecules very small carry a few to several hundred non essential genes AbR pathogenicity autonomously replicating 1000 copies cell Can be transferred from one bacterium to another intra inter species by multiple mechanisms Ribosomes Inside bacterial cell The molecular machine that assembles amino acids into proteins comprised of 54 proteins and 3 RNAs sufficiently different from Eukaryotic ribosomes target of many antibiotics There are antibiotics that are affect without disrupting human cells Endospores Metabolically inactive Dormant cell type produced mainly by Bacillus and Clostridium starvation response extraordinarily resistant to heat dessication toxic chemicals UV almost everywhere Very tough can remain dormant viable for 100 years botulism tetanus gas gangrene anthrax oooh my Endospores hardiest of all life forms capable of withstanding extremes in heat drying freezing radiation and chemiclas that would readily kill ordinary cells