LEC 7 BACT ANAT & PHYSIO- STRUCTURE & FUNCTION 2.0 PDF

PROCARYOTIC VS EUCARYOTIC BACTERIAL ANATOMY AND PHYSIOLOGY: STRUCTURE AND FUNCTION CELLULAR MORPHOLOGY & ARRANGEMENT OF BACTERIA AZLIN SHAM RAMBELY DEPARTMENT OF MEDICAL LABORATORY TECHNOLOGY FACULTY OF HEALTH SCIENCES...

PROCARYOTIC VS EUCARYOTIC BACTERIAL ANATOMY AND PHYSIOLOGY: STRUCTURE AND FUNCTION CELLULAR MORPHOLOGY & ARRANGEMENT OF BACTERIA AZLIN SHAM RAMBELY DEPARTMENT OF MEDICAL LABORATORY TECHNOLOGY FACULTY OF HEALTH SCIENCES UNIVERSITI TEKNOLOGI MARA (UITM)  Upon completion of this course, students will: LEARNING OUTCOMES Understand the range of prokaryotic and eukaryotic organisms that are considered to be microorganisms Be able to explain the components and cellular structure of bacterial cells.  PROKARYOTES VS EUKARYOTES “karyotic”- refers to nucleus, a membrane enclosed @ membrane bound cellular structure containing genetic material Prefix “Eu” – means “true” in Greek  EUKARYOTIC CELLS Recognized by the presence of a membrane-enclosed nucleus Larger than prokaryotic cells Structurally complex organisms Contain a variety of other organelles (specialized cellular structures enclosed by membrane & perform specific function) E.g. fungi, protozoa, algae  PROKARYOTIC CELLS Do not have a well-defined nucleus (genetic material- nucleoid) Less complex organisms (having simple structure with a rigid cell walls) Smaller than eukaryotic cells Lack bound organelles E.g. bacteria PROKARYOTIC VS. EUKARYOTIC CELLS Prokaryotic cells: Eukaryotic Cells: Do not have well Membrane- bound defined nucleus nucleus No Organelles Organelles Cell Wall of If cell wall, peptidoglycan Cellulose or chitin Binary Fission Mitosis  THE STRUCTURE OF PROKARYOTIC CELLS PROKARYOTIC CELL  THE STRUCTURE OF EUKARYOTIC CELLS EUKARYOTIC CELL  Three fundamental MORPHOLOGY shape: OF Coccus (spherical) PROKARYOTIC CELLS Bacillus (rod shape) Spiral COCCUS (COCCI) BACILLUS (BACILLI) SPIRAL  Prokaryotic cells may vary from groupings after cell division MORPHOLOGY vcells adhere together after cell division for OF characteristic arrangements PROKARYOTIC - arrangement depends on plane of CELLS division - especially in the cocci  Division along a single plane may result in pairs or chain of cells vPairs = diplococci - eg: Neisseria gonorrhoeae vChains = streptococci - eg: species of Streptococcus  Division along two @ three perpendicular planed will form cubical packets - eg: Sarcina genus  Division along several random planes will form clusters - eg: species of Staphylococcus MORPHOLOGY OF PROKARYOTIC CELLS  (i) Cocci diplococci streptococci tetrads staphylococci (ii) bacilli ARRANGEMENT diplobacilli streptobacilli coccobacilli (iii) spiral vibrio spirilla spirochete ARRANGEMENTS OF COCCI Diplococcus- cocci arranged in pairs Streptococcus: cocci arranged in chain A tetrad: cocci arranged in squares of 4 Staphylococcus: cocci arranged in irregular, often grape-like clusters ARRANGEMENTS OF BACILLI Bacillus: single bacilli Streptobacillus: bacilli arranged in chains  ARRANGEMEN TS OF SPIRAL Spirals come in one of three forms vibrio, spirillum, or spirochete Vibrio: a curved or comma- shaped rod SPIRILLUM: A THICK, RIGID SPIRAL Spirochete: a thin, flexible spiral  Structurally, a typical bacterium usually consists of: (i) appendages (external structure)- attachments to the cell surface in STRUCTURE & the form of flagella and pili (or FUNCTION OF fimbriae); PROCARYOTIC CELLS (ii) cell envelope consisting of a capsule, cell wall and plasma membrane; (iii) cytoplasmic region- contains the cell genome (DNA), ribosomes & various sorts of inclusions.  filamentous protein structures (flagellin) attached to the cell surface arises from the plasma membrane & protrudes through the cell wall Responsible for motility (that provide the swimming movement) @ motility organ FLAGELLA - use propeller-like movement to push bacteria - can rotate more than 100,000 revolutions/minute (82 miles/hour) Some important in bacterial pathogenesis - Helicobacter pylori penetration through mucous coat FLAGELLA  peritrichous (flagella distributed over FOUR the entire cell surface) BASIC lophotrichous (two @ more flagella TYPES OF FLAGELLA: at one or both ends) monotrichous (one flagellum) arising from one end amphitrichous (one flagellum at each end) FOUR BASIC TYPES OF FLAGELLA: Monotrichous flagellum of Vibrio cholerae Spirillum with amphitrichous arrangement of flagella single flagellum at each pole (arrows). Spirillum with lophotrichous arrangement of flagella bundle of flagella at each pole (arrows). Flagella stain of proteus showing peritrichous arrangement of flagella bacterium is surrounded by flagella (arrow).  Techniques to demonstrate bacterial motility: 1. flagellar stains - outline flagella and show their pattern of distribution. 2. motility test medium - demonstrates if cells can swim in a semisolid medium. 3. direct microscopic observation of living bacteria in a wet mount shows transient movement of swimming bacteria. HANGING DROP METHOD  short, hair-like structures on the surfaces of procaryotic cells Like flagella, they are composed of FIMBRIAE (PILI) protein shorter and stiffer than flagella, and slightly smaller in diameter used for attachment (not motility) & conjugation (mechanism of DNA transfer)  two basic types of pili: 1) short attachment pili (common pili), FIMBRIAE also known as fimbriae (PILI) 2) long conjugation pili, also called "F" or sex pili F or sex pilus- mediates the transfer of DNA during the process of conjugation Common pili- involved in specific adherence (attachment) of procaryotes to surfaces in nature Bacterial Pili Conjugation (Sex) Pilus  CELL ENVELOPE descriptive term for the three layers of material that envelope or enclose the protoplasm (cytoplasm) of the cell. cell protoplasm (cytoplasm) is surrounded by the plasma membrane, a cell wall and a capsule  Bacterial cell wall: Outer covering of most bacterial Rigid structure Surrounds cytoplasmic membrane Determines shape of bacteria CELL WALL Holds cell together Is an essential structure that protects the cell protoplast from mechanical damage and from osmotic rupture or lysis/prevent cell from bursting  Unique chemical structure- distinguishes Gm +ve from Gm –ve bacteria Main structural component – peptidoglycan (@ CELL WALL murein): thick in Gram-positive bacteria & thin in Gram-negative Thickness of the peptidoglycan accounts for the ability/lack of ability to retain the crystal violet used in the Gram stain  Peptidoglycan component consists of 2 types of sugar: - N-acetylglucosamine (NAG) - N-acetylmuramic acid (NAM) with a pentapeptide coming off of the NAM Joined subunits form glycan chain Glycan chain held together by string of four amino acid The Peptidoglycan Monomer of The Peptidoglycan Monomer of Escherichia coli Staphylococcus aureus GRAM-POSITIVE CELL WALL May consists of up to 40 layers of peptidoglycan 90% of the Gram-positive cell wall is comprised of peptidoglycan (10 x the thickness of a Gram- negative cell wall) Also contain polysaccharide molecule – teichoic acid TEICHOIC ACID üSugar-containing polymers üextend from the plasma membrane through the peptidoglycan cell wall üAssist in maintaining cell shape & play a role in cell division üHelp some Gram positive bacteria to infect cells & cause disease GRAM-NEGATIVE CELL WALL Also composed of peptidoglycan (much thinner – a couple of layers, being comprised of only 20% peptidoglycan) More complex than Gm+ve cell wall Peptidoglycan sandwiched between outer membrane & cytoplasmic membrane Region between outer membrane & cytoplasmic membrane is called periplasm - most secreted proteins contained here - proteins of ABC (ATP binding cassette) transport system located here Profiles of the cell envelope of the Gram-positive and Gram-negative bacteria: The Gram-positive wall is a uniformly thick layer external to the plasma membrane. It is composed mainly of peptidoglycan (murein). The Gram-negative wall appears thin and multilayered. It consists a relatively thin peptidoglycan sheet between the plasma membrane and a phospholipid-lipopolysaccharide outer membrane. The space between the inner (plasma) and outer membranes (wherein the peptidoglycan resides) is called the periplasm. GRAM- NEGATIVE CELL WALL GRAM- NEGATIVE CELL WALL  Mycoplasma - genus of naturally occuring bacteria which lack cell walls L-forms - cell-wall deficient forms of bacteria usually BACTERIA WITH produced in the lab but sometimes DEFICIENT CELL spontaneously form in the body of patient’s WALL treated with penicillin Protoplasts - derived from Gm +ve bact; cell wall lost due to the action of lysozyme enzyme which destroy PTD Spheroplasts - derived from Gm –ve bact  lies internal to the cell wall CYTOPLASMIC and encloses the cytoplasm MEMBRANE of the bacterium (CELL Delicate thin fluid structure MEMBRANE @ PLASMA Surrounds cytoplasm of cell MEMBRANE) Defines boundary CYTOPLASMIC MEMBRANE 2 structural component double layer of phospholipids Proteins CYTOPLASMIC MEMBRANE  retains the cytoplasm, particularly in cells without cell walls & separates (the cell) from CYTOPLASMIC the surroundings MEMBRANE also serves as a selectively permeable barrier: it allows particular ions and molecules to pass, either into or out of the cell, while preventing the movement of others  1. Selective barrier (selectively permeable) 2. Secretes exoenzymes FUNCTIONS amylases OF CELL lipases MEMBRANE peptidases CAN NOT UNDERGO PHAGOCYTOSIS LAYERS EXTERNAL TO CELL WALL  extensive bacterial glycocalyx (substances that surround bacterial cells) CAPSULE appears as an extensive, tightly bound accumulation of gelatinous material adhering to the cell wall  Contribute to virulence of bacteria by preventing phagocytosis by WBC’s Prevents drying out or dessication FUNCTIONS OF Allows bacteria to adhere to various CAPSULES surfaces Streptococcus mutans - enamel on teeth to cause dental carries Klebseilla pneumoniae - attaches to respiratory tract DIPLOCOCCI SURROUNDED BY CAPSULES  Outer surface of the cell For encapsulated strains- lies just underneath the capsule consisting of phospholipids, various OUTER membrane proteins, lipoproteins, MEMBRANE and lipopolysaccharide that is found surrounding the cell wall of Gram-negative bacteria  Gram-positive bacteria lack an outer membrane most important outer membrane function is to serve as a protective barrier ( It prevents or slows the entry of bile salts, antibiotics, and other toxic substances that might kill or injure the bacterium)  is a volume found between the bacterial plasma membrane and cell PERIPLASMIC wall SPACE Occurs only in Gram-ve bacteria INTERNAL STRUCTURES INTERNAL STRUCTURES INTERNAL STRUCTURES- 1 circular chromosome NUCLEAR (ccDNA) AREA (NUCLEOID) attached to a mesosome - segragation of DNA during binary fission  Small circular, extra-chromosomal pieces of DNA INTERNAL 5 to 100 genes STRUCTURES- Code for auxiliary metabolic functions: PLASMIDS antibiotic resistance penicillase production of toxins E. coli 0157:H7 INTERNAL STRUCTURES- RIBOSOME INTERNAL STRUCTURES INTERNAL STRUCTURES- ENDOSPORES  Body that allows the organism to resist adverse INTERNAL condition (formed under STRUCTURES- periods of environmental ENDOSPORES stress) Only found in Gram (+) Bacteria (genus Bacillus, Clostridium)  Extremely resistant to heat, cold, chemicals, lack of water, etc. Most vegetative bacterial cells are killed at temps. above 70° C (160° F) ENDOSPORES Endospores can survive boiling water for several hours (some for as long as 20 hours) ENDOSPORE STAIN OF BACILLUS MEGATERIUM Note green endospores within pink bacilli. ENDOSPORE STAIN OF CLOSTRIDIUM TETANI Note the endospore within the rod gives the bacterium a "tennis racquet" shape (arrows). ENDOSPORES