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internet Review the Todar"s digital Textbook of Bacteriology. "The Good, the Bad, and also the Deadly" tag words: bacterial structure, flagellum, flagella, pilus, pili, fimbriae, capsule, S-layer, glycocalyx, slime layer, biofilm, external membrane, LPS, cabinet wall, peptidoglycan, murein, teichoic acid, plasma membrane, cell membrane, phospholipid bilayer, deliver system, proton engine force, pmf, ATPase, DNA, chromosome, nucleoid, ribosome, 30S subunit, 50S subunit, 16S rRNA, inclusion, PHB, glycogen, carboxysome, endospore, parasporal crystal.

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Structure and duty of Bacterial cells (page 1)(This chapter has actually 10 pages)© Kenneth Todar, PhD
drawing of a typicalbacterial cell, by Vaike Haas, college of Wisconsin-Madison
Primary framework ofBiological Macromolecules identify FunctionProcaryotic structural components consistofmacromoleculessuch together DNA, RNA, proteins, polysaccharides, phospholipids, or somecombinationthereof. The macromolecules are consisted of of major subunits together asnucleotides, amino acids and sugars (Table 1). It is thesequence in which thesubunits are placed together in the macromolecule, called the primarystructure,that determines many of the properties that the macromoleculewillhave. Thus, the hereditary code is determined by specific nuleotide basesequences in chromosomal DNA; the amino acid sequence in a proteindetermines the nature and function of the protein; and sequence ofsugars in bacterial lipopolysaccharides determines unique cell wallproperties because that pathogens. The major structure that amacromolecule will drive that function, and also differences withinthe main structure of organic macromoleculesaccounts because that the tremendous diversity that life.Table 1.Macromoleculesthat comprise cell product



Wherefoundin cell


amino acids

Flagella, pili, cell walls,cytoplasmicmembranes, ribosomes, cytoplasm


sugars (carbohydrates)

capsules, inclusions(storage), cell walls


fatty acids


Nucleic Acids(DNA/RNA)


DNA: newly closed (chromosome),plasmidsrRNA: ribosomes; mRNA, tRNA: cytoplasm

ProcaryoticCell Architecture

At one time the wasthought the bacteriaand various other procaryotes were essentially "bags of enzymes" v noinherent cellulararchitecture. Thedevelopment of the electron microscope in the 1950s revealed thedistinct anatomical functions of bacteria and also confirmed the suspicionthat castle lackeda nuclear membrane. Procaryotes space cells ofrelativelysimple construction, specifically if contrasted to eucaryotes. Whereaseucaryoticcells have a preponderance of oribelles with separate cellularfunctions,procaryotes carry out all cellular functions as separation, personal, instance units.

Aprocaryoticcell has actually five essential structural components: a newly closed (DNA),ribosomes,cellmembrane, cell wall, and some sort of surface layer,whichmay or might not it is in an inherent component of the wall.

Structurally,there arethree architectural regions: appendages (attachments come thecell surface)in the kind of flagella and pili (or fimbriae); a cellenvelope consisting of a capsule, cell wall and also plasmamembrane; and a cytoplasmic region that includes the cabinet chromosome(DNA) and ribosomes and also various species of inclusions(Figure 1).


Figure 1.Cutaway illustration of a typicalbacterial cell portraying structural components. View Table 2belowfor chemistry composition and function of the labeling components.

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Table2. Summary of characteristicsof common bacterial cell structures
Structure Flagella Function(s) swim movement

Predominant chemicalcomposition


Sex pilus Stabilizes matingbacteria during DNA carry by conjugation Protein
Common chili or fimbriae Attachment come surfaces;protectionagainst phagotrophic engulfment Protein
Capsules (includes"slimelayers" and glycocalyx) Attachment come surfaces;protectionagainst phagocytic engulfment, sometimes killing or digestion;reserveof nutrients or protection versus desiccation Usually polysaccharide;occasionallypolypeptide
Cell wall
Gram-positive bacteria Prevents osmotic lysisof cellprotoplast and confers rigidity and shape ~ above cells Peptidoglycan (murein)complexedwith teichoic acids
Gram-negative bacteria Peptidoglycan preventsosmoticlysis and also confers rigidity and shape; external membrane is permeabilitybarrier;associated LPS and also proteins have actually various functions Peptidoglycan (murein)surroundedby phospholipid protein-lipopolysaccharide "outer membrane"
Plasma membrane Permeability barrier;transportof solutes; energy generation; location of plenty of enzyme systems Phospholipid and also protein
Ribosomes Sites that translation(protein synthesis) RNA and also protein
Inclusions Often to make reservation ofnutrients; additionalspecialized functions Highly variable;carbohydrate,lipid, protein or inorganic
Chromosome Genetic product ofcell DNA
Plasmid Extrachromosomalgenetic material DNA

Figure2 . Electron micrographof one ultra-thin ar of a dividing pair of group A streptococci(20,000X).The cell surface fimbriae (fibrils) areevident.The bacter cell wall isseen as the light staining region between the fibrils and also the darkstainingcell interior. Cell department in development is shown by the brand-new septumformed between the 2 cells and also by the indentation the the cell wallnearthe cell equator. The streptococcal cabinet diameter is equal toapproximatelyone micron. Electron micrograph the Streptococcus pyogenes byMariaFazio and also Vincent A. Fischetti, Ph.D. Through permission. TheLaboratory of bacter Pathogenesis and Immunology, RockefellerUniversity. thing continuedNext Page© Kenneth Todar, Ph.D. All civil liberties reserved. - www.rebab.net