The Building blocks of a bacterial cell by E. Börje Lindström This learning object has been funded by the European Commissions FP6 BioMinE project

Cell types prokaryotes:- bacteria - archeons eukaryotes:- yeast - algae - fungi - plant - animal

Bacteria General aspects Bacteria exist in many different forms and sizes. Forms: - sphericale.g. Staphylococcus aureus -curved Spirilles and spirochetes or helical - rod shapede.g. Escherichia coli Sizes: 1  m 1- 2  m Depending on growth media!

General aspects, cont. Weight (dry): ~ – g Volume: ~ ml Aggregates: - Especially among cocci - diplococci - streptococci - staphylococci - tetrads

The Bacterial Cell - Schematic Cell wall Cytoplasm membrane Cytoplasm

In the cytoplasm most of the biosynthesis of the cell occur. It is a suspension of: small soluble molecules -buildingblocks for macromolecules e.g. aa, metal salts etc. macro molecules - protein/enzymes, RNA etc. particles - ribosomes, granula etc.

ProkaryotsEykaryotes Membrane -+ Endoplasmic reticulum - Cromosome(s) + 1>1 closedopen DNA (1 molecule) DNA + proteins (histones) Cytoplasm, cont. The ’nucleus’ - a comparison Slow growth – 1-2 copies of the chromosome Rapid growth – 2-5 copies

Cytoplasm, cont. Ribosomes - nucleoproteins = rRNA + proteins - function in protein synthesis Prokaryotes Eukaryotes 2 subunits 30S 50S 40S 60S 16S rRNA + 21 diff. prot 23S rRNA + 34 diff. prot 18S rRNA + ?? diff. prot 28S rRNA + ?? diff. prot 70S80S

Cytoplasm membrane Function: - selective permeability barrier - transport mechanisms - electron transport chain Properties: -unit membrane of phospholipids - ~8 nm thick - hydrofilic (glycerol) outer part - hydrophobic (fatty acids) inner part - protein inbedded (transport) - a ’floating’ structure, stabilized with Mg 2+ and Ca 2+

Cell Wall Constitute ~ 10-20% of the dry weight of the baterium almost all prokaryotes have a cell wall Funktion: - a mechanical protection - gives the cell its form Strength: - due to special chemical structures in all types of cells cellulose – plants chitin – fungi mucopeptides (murein) - eubacteria

Cell Wall, cont. The murein structure a net work around the cell carbohydrates peptides

Cell Wall, cont. Chain of carbohydrates: -alternating amin suger - NAG, N-acetyl glucoseamin - NAM, N-acetyl muramic acid NAM – NAG – NAM – NAG – NAM – NAG L-ala D-glu L-lys D-ala NAM – NAG – NAM – NAG – NAM – NAG (D-ala) D-ala L-lys D-glu L-ala (aa) n Peptide bond aa with two amino groups (alternative DAP)

Gram staining Heat fixation of the cells (on a object glass) + crystal violet (blue dye) + I 2 -KI All cells blue + aceton/alcohol Blue cellsDestained cells, grayish + safranin (red dye) G+, blue/violett cells G-, red cells

Components of the cell wall ComponentGram +Gram - Murein, mucopeptide  nm  10 nm Teichoic acid (PO 4 -rich) +- Lipoprotein -+ Lipopolysccharide (LPS) -+ Proteins (+) Summary:

Lysozyme treatment NAM – NAG – NAM – NAG – NAM – NAG lysozyme G+: - protoplast formation, cell wall completely removed G-: - spheroplast formation, part of the cell wall left

Granula Storage of energy and carbon sources - Glykogen - Starch -  -hydroxybutyrate Others -Polyphosphates - elementar sulphur

Cell surface structures Pili/ fimbriae: - only in G - -short protein tube - Ø ~ 7 nm - helical structure - several types e.g. F-pili - Function - involved in adherence to surfaces Flagella: -motility organ - thin (~ 20 nm) long protein molecules - polar or peritrichious

Bacterial spores A heat resistant form of the cell (endospore) 1 cell1 spore1 cell Found only in Bacillus (aerob) and Clostridium (anaerob)

Capsules and slime layers Usually a polysaccharide or protein layer excreted from the cell Function: -attachement to surfaces - protection against phagocytosis