Unit 3 Structure of Bacteria and Archaea PDF

Cells of Bacteria and Archaea SHAIRA DAWN G. OAQUERA Faculty, DBS COLLEGE OF ARTS & SCIENCES Department of Biological Sciences COLLEGE OF ARTS & SCIENCES Department of Biological Sciences EUKARYOTES VS PROKARYOTES CELL SIZE The average diameter of spherica...

Cells of Bacteria and Archaea SHAIRA DAWN G. OAQUERA Faculty, DBS COLLEGE OF ARTS & SCIENCES Department of Biological Sciences COLLEGE OF ARTS & SCIENCES Department of Biological Sciences EUKARYOTES VS PROKARYOTES CELL SIZE The average diameter of spherical bacteria is 0.5-2.0 µm. For rod-shaped or filamentous bacteria, length is 1-10 µm and diameter is 0.25-1.0 µm.  Surface-to-volume ratio (S/V) CELL SIZE The surface area and volume determine the cell size and both play an important role in a cell’s exchange of materials Small cells have more surface area relative to cell volume = higher surface-to-volume ratio BACTERIAL CELL MORPHOLOGY According to SHAPE Coccus – spherical or ovoid shape Rod/bacillus – cylindrically shaped cell Spirilla – spiral shapes BACTERIAL CELL MORPHOLOGY According to ARRANGEMENT: Monococcus – singular cocci Diplococcus/bacilli – two spherical/rod arranged in pairs Streptococcus/bacilli – cocci/bacilli form in long chains Staphylococcus – grapelike clusters Sarcina – three-dimensional cubes (consist of eight cells) Tetrad – arranged in a group of 4 cocci cells. Coccobacillus – short round rod BACTERIAL CELL MORPHOLOGY Unusual shapes: Vibrio – curved rod Spirochetes – tightly coiled bacteria Appendaged bacteria – possess extensions of cells as long tubes or stalks Star-shaped bacteria (Stella) Square shape (Haloarcula) BACTERIAL CELL STRUCTURE  BACTERIAL CELL STRUCTURE Structures common Structures found in Structures found in to all bacterial cells most bacterial cells some bacterial cells Cell membrane Cell wall Flagella Cytoplasm Surface coating or Pili Ribosomes glycocalyx Fimbriae One (or a few) Capsules chromosomes Slime layers Inclusions Actin cytoskeleton Endospores  BACTERIAL CELL STRUCTURE Cytoplasm Contents: Gelatinous solution Site for many biochemical and synthetic activities 70%-80% water Also contains larger, discrete cell masses (chromatin body, ribosomes, granules, and actin strands) Location of growth, metabolism, and replication  BACTERIAL CELL STRUCTURE Plasma membrane Surrounds the cytoplasm and separates it from the environment Function as a selective permeability Consists of glycerol group (hydrophilic head) and fatty acids (hydrophobic tail) by ESTER Linkage A phospholipid bilayer containing embedded proteins  BACTERIAL CELL STRUCTURE Plasma membrane A variety of proteins are attached to or integrated into the cytoplasmic membrane: INTEGRAL MEMBRANE PROTEINS: embedded in the membrane PERIPHERAL MEMBRANE PROTEINS: more loosely attached Important properties: ability to regulate transport across cellular boundaries permeable to specific ions and a variety of polar molecules  ARCHAEAL CELL STRUCTURE Archaeal membranes Consists of the glycerol group and isoprene (hydrophobic side chain) by ETHER bonds Constructed from either a phytanyl group or a biphytanyl group In the tetraether lipid structure, the ends of the inwardly pointing phytanyl groups are covalently linked at their termini to form a lipid monolayer – resistant to heat  CELL STRUCTURE Functions of the Plasma membrane  BACTERIAL CELL STRUCTURE Cell wall Functions: Withstand pressure Protection against osmotic lysis Confer shape and rigidity  BACTERIAL CELL STRUCTURE THIN Cell wall PEPTIDOGLYCAN THICK PEPTIDOGLYCAN  BACTERIAL CELL STRUCTURE Peptidoglycan Structure  BACTERIAL CELL STRUCTURE Lysozyme A protein that cleaves β-1,4- glycosidic bonds in peptidoglycan act as antibiotics  BACTERIAL CELL STRUCTURE Gram-positive cell wall Composed of 90% peptidoglycan TEICHOIC ACID: acidic molecules embedded in the cell wall Covalently bonded to muramic acid in the peptidoglycan LIPOTEICHOIC ACID: certain teichoic acids covalently bound to membrane lipids  BACTERIAL CELL STRUCTURE Gram-negative cell wall Outer membrane Consist of Lipopolysaccharide (LPS) and Thin peptidoglycan  BACTERIAL CELL STRUCTURE Gram-negative cell wall Outer membrane Consist of Lipopolysaccharide (LPS) and Thin peptidoglycan confers only modest structural strength on the gram-negative cell Peptidoglycan: major strengthening agent acts as an effective barrier against many lipophilic antibiotics and other harmful agents that might otherwise penetrate the cytoplasmic membrane.  BACTERIAL CELL STRUCTURE Gram-negative cell wall Outer membrane Consist of Lipopolysaccharide (LPS) as endotoxin Endotoxins (LPSs) are molecules that elicit strong immune response. LPSs have a high heat stability, hence, quite impossible to destroy under regular sterilizing conditions Involved in infection, contributing to symptoms such as fever, hemorrhaging,and septic shock  BACTERIAL CELL STRUCTURE Bacterial Endotoxin vs Exotoxin 1. Endotoxins are lipopolysaccharides, while exotoxins are soluble proteins which can act as enzymes. Both are produced by pathogenic bacteria 2. Both Gram-negative and Gram-positive bacteria produce exotoxins, while endotoxins are produced by Gram-negative bacteria 3. Endotoxins cannot act as enzymes, but exotoxins can act as enzymes 4. Endotoxins are a part of the outer membrane of cell wall in Gram-negative bacteria, whereas exotoxins are extracellular (secreted) component 5. Endotoxins are less toxic than exotoxins 6. Exotoxins are specific to particular bacterial strain, while endotoxins are not 7. Exotoxins are not heat stable, whereas endotoxins are heat stable 8. Endotoxins are poor antigens, whereas exotoxins are highly antigenic 9. By stimulating the immune system exotoxins produce antitoxins to neutralize the toxin, while endotoxins do not produce antitoxins  ARCHAEAL CELL STRUCTURE Archaeal cell wall Contain PSEUDOMUREIN: a polysaccharide similar to peptidoglycan S-LAYERS  ARCHAEAL CELL STRUCTURE Archaeal cell wall S-LAYERS The most common type of cell wall in Archaea is the paracrystalline surface layer, or S-layer S-layers can form various symmetries: ✓ hexagonal, tetragonal, or trimeric sufficiently strong to withstand osmotic always the outermost wall layer; has direct contact with the environment  Application: Gram staining Crystal violet-iodine forms in cell Gram-positive Gram-negative Alcohol dehydrates peptidoglycan Alcohol dissolves outer membrane and Crystal violet-iodine do not leave leaves holes in peptidoglycan Crystal vuolet-iodine complex washes out  BACTERIAL CELL SURFACE STRUCTURE Glycocalyx = “sugar coat” Extracellular, made up generally of polysaccharide, polypeptide or combination of both (glycoprotein) Protects pathogenic species from phagocytosis by macrophages CAPSULE: adhere SLIME LAYER: loosely firmly to the cell wall attached to the cell wall  BACTERIAL CELL SURFACE STRUCTURE Flagella Tiny rotating machines that function to push or pull the cell through a liquid Gram-negative Gram-positive Test for Motility Needle with cells stabbed in tubes with motility test medium (gelatin) - Post-incubation - Bacterium on left is non-motile; the one in tube on right is motile Basal body with 2 pairs of rings Basal body with only 1 pair of rings  BACTERIAL CELL SURFACE STRUCTURE Flagella Flagellin: protein found in the filament of a bacterial flagellum Hook: a wider region at the base of the filament Flagellum motor: anchored in the CM and cell wall; consists of a central rod that passes through a series of rings: L ring: an outer ring, anchored in the LPS layer in gram- negative bacteria Gram Negative P ring: second ring, anchored in the peptidoglycan layer of the cell wall Gram Positive MS and C rings: located within the CM and the cytoplasm, respectively. Mot proteins: surrounding the inner rings to generate torque. Fli proteins: function as the motor switch Proton Motive Force: energy required for the flagellar rotation  BACTERIAL CELL SURFACE STRUCTURE Flagellar arrangement Peritrichous: Monotrichous: flagella are inserted a single polar at many locations flagellum at one end around the cell or the other surface. Amphitrichous: a Lophotrichous: tuft of flagella a group of flagella emerges from both (tuft) may arise at poles of the cell. one end of the cell.  BACTERIAL CELL SURFACE STRUCTURE Flagellar movement Forward motion then change in direction Change in direction by: pulling the cell instead of pushing by CW rotation  ARCHAEAL CELL SURFACE STRUCTURE several different filament makes up the filament can be considered a rotating type IV pilus capable of both clockwise and counterclockwise rotation Rotation of the archaellum is driven by the hydrolysis of ATP.  BACTERIAL CELL SURFACE STRUCTURE Fimbriae (Filamentous Proteins) Extracellular, filaments much shorter (3-10 nm) than flagella Function: adhesion to host cell or surface of substrate ✓ Adhesion is by a lock-and-key type of bonding of various bacterial “adhesins” to complimentary receptors on the surface of host cell Adhesins – chemical components of bacterial glycocalyx, cell walls, pili Host’s receptors – usually glycoproteins located on cell membrane or tissue surface or fimbriae  BACTERIAL CELL SURFACE STRUCTURE Pili ✓ longer than fimbriae ✓ Receptors for certain types of viruses ✓ facilitates genetic exchange (conjugation) ✓ Mediate genetic transfer (transformation) ✓ enabling adhesion of pathogens to specific host tissues Type IV pili: support cell movement called twitching motility o type of gliding motility: movement along a solid surface present only at the poles of rod-shaped cells  BACTERIAL CELL STRUCTURE Inclusion Bodies: Energy reserves CARBON STORAGE POLYMERS Poly-β-hydroxybutyrate (PHB): most common carbon-based inclusion bodies in prokaryotic organisms; a lipid that is formed from β-hydroxybutyric acid units Poly-β-hydroxyalkanoate (PHA): carbon- and energy-storage polymers Glycogen: polymer of glucose Reservoir of both carbon and energy accumulation occurs in the stationary growth phase in response to excess C when N, S, or P is limiting  BACTERIAL CELL STRUCTURE Inclusion Bodies: Energy reserves POLYPHOSPHATE, SULFUR, AND CARBONATE MINERALS Polyphosphate: inorganic phosphate accumulation forming granules degraded and used as sources of phosphate for nucleic acid and phospholipid biosynthesis Sulfur globules: elemental sulfur that accumulates inside the cell when hydrogen sulfide is oxidized. Carbonate minerals form inside the cell of some Sulfur cyanobacteria Gleomargarita: forms benstonite that contains barium, strontium, and magnesium Biomineralization: microbiological process of forming minerals  BACTERIAL CELL STRUCTURE Inclusion Bodies: Magnetosomes Some bacteria can orient themselves within a magnetic field because they contain magnetosomes impart a magnetic dipole on a cell, allowing it to orient itself in a magnetic field. Magnetotaxis: process of migrating along Earth’s magnetic field lines Enclosed by a thin membrane: Sulfur functional as they catalyze iron precipitation during magnetosome synthesis.  BACTERIAL CELL STRUCTURE Inclusion Bodies: Gas vacuoles Confer buoyancy Conical-shaped structures, hollow yet rigid and of variable length and diameter Cyanobacteria and algae form massive accumulations called blooms in lakes or other bodies of water. ]  BACTERIAL CELL STRUCTURE Inclusion Bodies: Endospore highly differentiated cells that are extremely resistant to heat, harsh chemicals and radiation. Functions: survival structures, to endure unfavorable growth conditions. Dormant stage of a bacterial life cycle: vegetative cell – endospore – vegetative cell. Endospore-forming bacteria (Bacillus spp.) are commonly found in soil. Malachite green: used to stain endospore  BACTERIAL CELL STRUCTURE Inclusion Bodies: Endospore Exosporium: a thin protein covering on the outermost layer of the endospore. Spore coats: composed of spore- specific proteins (second layer). Cortex: next to spore coat which consists of loosely cross-liked peptidoglycan. Core: inside the cortex, which contains the core wall, CM, cytoplasm, nucleoid, ribosomes and other cellular essentials.  BACTERIAL CELL STRUCTURE Inclusion Bodies: Endospore  BACTERIAL CELL STRUCTURE Two subunits: Ribosomes ✓ smaller subunit (SSU) binds to mRNA ✓ larger subunit (LSU) binds to the tRNA and the amino acids. Prokaryotes = 70S ribosomes 50S (LSU) – has 23S RNA (2900 nucleotides), 5S RNA (120 nucleotides) and 34 proteins 30S (SSU) – has 16S RNA (1540 nucleotides) bound to 21 proteins Eukaryotes = 80S ribosomes 60S (LSU) – has 28S RNA (4700 nucleotides), 5.8S RNA (160 nucleotides), 5S rRNA (120 nucleotides), and 46 proteins 40S (SSU) – has 18S RNA (1900 nucleotides and 33 proteins  GENETIC MATERIAL OF BACTERIA: DNA Essential functions of genetic material: replication and expression. contained in a single circular molecule = “Bacterial chromosome” NUCLEOID: irregular shape of chromosomes o sits in the cytoplasm, no envelope  GENETIC MATERIAL OF BACTERIA: DNA Characteristic Prokaryotes Eukaryotes Chromosomes Usually only one, hence, Generally in multiples Number (ploidy) haploid of two, hence, diploid Generally circular with no Shape Generally linear free ends Extrachromosomal Usually present (plasmids) Generally absent circular linear Introns (non-coding (in prokaryote) (in eukaryote) Generally absent Present for protein) Number of gene in One Two chromosome Replication & Replication, transcription Transcription in the Gene action and translation in nucleus, cytoplasm Translation in cytoplasm Clustered as operons (i.e. Mode of gene genes transcribed and Genes not clustered transcription translated based on one in operons & translation mRNA)  GENETIC MATERIAL OF BACTERIA: DNA PLASMIDS: extrachromosomal units small circular DNA molecules o has its own ‘origin of replication’ and can copy itself independently making hundreds of copies o Structure: ✓ Ori represents where nucleotide sequence begins; ✓ antibiotic resistance indicates gene of interest to identify for selection of the plasmid ✓ polylinker represents the cloning sites, or a small piece of DNA into which a foreign DNA fragment can be inserted in cloning Picks up plasmids via conjugation or from the environment, can also easily lose them  Cells of Bacteria and Archaea EUKARYOTIC MICROBIAL CELLS SHAIRA DAWN G. OAQUERA Faculty, DBS SHAIRA DAWN G. OAQUERA Faculty, DBS COLLEGE OF ARTS & SCIENCES Department of Biological Sciences  EUKARYOTIC MICROORGANISMS The nucleus is universal and a hallmark of the eukaryotic cell. Mitochondria: nearly universal among eukaryotic cell. Chloroplasts: found only in phototrophic cells. Some microbial eukaryotes have flagella or cilia. A cell wall is present in fungi and algae.  EUKARYOTIC MICROORGANISMS The Nucleus The DNA is wounded around histones (basic proteins ) to form nucleosomes. Enclosed by a pair of membranes: The inner and outer nuclear membranes specialized in interactions with the nucleoplasm and the cytoplasm. Nuclear membranes contain pores for NUCLEAR TRANSPORT (proteins and nucleic acids. Nucleolus: site of rRNA synthesis Rich in RNA and ribosomal proteins exported to the cytoplasm.  EUKARYOTIC MICROORGANISMS Mitochondrion Site of aerobic respiration Enclosed by a double membrane system: ✓ outermost membrane: relatively permeable and contains pores that allow the passage of small molecules. ✓ innermost membrane: less permeable and closely resembles CM of Bacteria ▪ Cristae: folded internal membranes Contain enzymes for respiration and ATP production Contain transport proteins: regulate passage of ATP into and out of the matrix. ▪ Matrix: innermost compartment Contains enzymes for the oxidation of organic compounds (citric acid cycle)  EUKARYOTIC MICROORGANISMS Hydrogenosomes Some eukaryotic microorganisms live an anaerobic lifestyle: ✓ they lack mitochondria and may contain HYDROGENOSOMES: lack citric acid cycle enzymes lack cristae carry out a strictly fermentative metabolism. major biochemical reaction: oxidation of pyruvate to H2, CO2, and acetate  EUKARYOTIC MICROORGANISMS Chloroplast chlorophyll-containing organelles of phototrophic microbial eukaryotes (algae) function to carry out photosynthesis have a permeable outer membrane and a much less-permeable inner membrane. innermost membrane surrounds the STROMA ✓ contains the enzyme ribulose bisphosphate carboxylase (RubisCO), the key enzyme of the Calvin cycle. THYLAKOIDS: flattened membrane discs ✓ where Chlorophyll and all other components needed for ATP synthesis is located  EUKARYOTIC MICROORGANISMS Endoplasmic Reticulum network of membranes continuous with the nuclear membrane Two types: A. ROUGH ER: contains attached ribosomes ✓ Producer of glycoproteins ✓ Produces new membrane material B. SMOOTH ER: does not contain attached ribosomes ✓ participates in the synthesis of lipids ✓ Facilitates some aspects of carbohydrate metabolism.  EUKARYOTIC MICROORGANISMS Golgi Complex a stack of membrane-bound sacs called cisternae. products of the ER are chemically modified and sorted: ✓ Destined for secretion ✓ function in other membranous structures in the cell Modifications: glycosylations (addition of sugar residues) convert the proteins into glycoproteins -> targeted to specific locations in the cell.  EUKARYOTIC MICROORGANISMS Lysosomes membrane-enclosed compartments that contain digestive enzymes: hydrolyze proteins, fats, and polysaccharides FUNCTIONS: ✓ fuses with food that enters the cell in vacuoles ✓ releases digestive enzymes that break down the foods for biosynthesis and energy generation. ✓ degrade damaged cellular components and recycle them for new biosyntheses.  EUKARYOTIC MICROORGANISMS Cytoskeleton This internal support network consists: A. Microtubules: hollow tubes about composed of tubulin proteins ✓ maintain cell shape and cell motility by cilia and flagella ✓ move chromosomes during mitosis and in movement of organelles within the cell. B. Microfilaments : smaller than microtubules ✓ polymers of two intertwined strands of the protein actin. ✓ maintain or change cell shape: cell motility by cells that move by amoeboid movement, and during cell division. C. Intermediate filaments are fibrous keratin proteins that form into fibers ✓ maintain cell shape and position organelles in the cell.  EUKARYOTIC MICROORGANISMS Flagella and Cilia present on the surface of many eukaryotic microbes function as organelles of motility, CILIA: short flagella ✓ beat in synchrony to propel the cell (quite rapidly) through the medium. FLAGELLA: long appendages present singly or in groups ✓ propel the cell along (more slowly) — through a whiplike motion structurally quite distinct from bacterial flagella (contain microtubules) do not rotate as do the flagella and archaella  EUKARYOTIC MICROORGANISMS Flagella and Cilia Get in Touch With Us Send us a message or visit us City of Batac, Ilocos Norte, Philippines (63) 77-600-0459 [email protected] Follow us for updates facebook.com/MMSUofficial www.mmsu.edu.ph