Download STRUCTURE AND FUNCTION OF PROKARYOTES

STRUCTURE AND FUNCTION OF
PROKARYOTES-PART 1
DR NAZIA KHAN
ASSISTANT PROFESSOR
OBJECTIVES:
1. CLASSIFY AND DEFINE EUKARYOTES AND PROKARYOTES
2. DESCRIBE DIFFERENT STRUCTURES OF PROKARYOTE CELL AND THE
FUNCTIONS OF EACH STRUCTURE
3. CLASSIFY BACTERIA AND BRIEFLY DISCUSS VARIOUS METHODS OF
CLASSIFICATION
WHAT ARE PROKARYOTES AND EUKARYOTES
• BELONG TO KINGDOM PROTISTA WHICH IS DIVIDED INTO
PROKARYOTES AND EUKARYOTES
• DIFFERENCES BETWEEN PROKARYOTES AND EUKARYOTES
examples
Bacteria and alga
fungi, higher plants, animals
• PROKARYOTES DON’T HAVE A MEMBRANE-BOUND NUCLEUS
• THREE FUNDAMENTAL CHARACTERISTICS ARE OFTEN
CONSIDERED TO DISTINGUISH PROKARYOTES FROM
EUKARYOTES:
i.
SMALL SIZE
ii. ABSENCE OF A COMPLEX, ORGANELLE CONTAINING
CYTOPLASM
iii. ABSENCE OF A NUCLEAR MEMBRANE
PROKARYOTES
• PROKARYOTIC SMALLER THAN EUCARYOTIC CELLS
• PROKARYOTES ARE VERY SIMPLE CELLS UNLIKE EUCARYOTIC
CELLS
• THE CYTOPLASM OF PROCARYOTIC CELLS IS NOT FILLED WITH
INTERNAL MEMBRANES. THE CYTOPLASM IS SURROUNDED BY A
CELL MEMBRANE, A CELL WALL (USUALLY), AND SOMETIMES A
CAPSULE OR SLIME LAYER
• BINARY FISSION—THE SIMPLE DIVISION OF ONE CELL INTO
TWO CELLS, AFTER DNA REPLICATION AND THE FORMATION OF
A SEPARATING MEMBRANE AND CELL WALL.
1.
THE OUTER LAYER OR CELL ENVELOPE
• CELL MEMBRANE
• BACTERIAL CELL WALL
2.
CELLULAR APPENDAGES:
• GLYCOCALYX (SLIME LAYERS AND CAPSULES)
• FLAGELLA
• PILI (FIMBRIAE)
3.
OTHER STRUCTURES:
• CYTOPLASM
• CYTOPLASMIC PARTICLES (RIBOSOMES)
• CHROMOSOME
• SPORES (ENDOSPORE
CELL MEMBRANE, PLASMA, CYTOPLASMIC, OR CELLULAR MEMBRANE
• ENCLOSES THE CYTOPLASM OF A PROKARYOTIC CELL
• IT CONSISTS OF PROTEINS AND PHOSPHOLIPIDS.
• IT IS FLEXIBLE AND SO THIN THAT IT CANNOT BE SEEN WITH A COMPOUND LIGHT MICROSCOPE.
FUNCTION:
1.
SELECTIVELY PERMEABLE
2.
MANY ENZYMES ARE ATTACHED TO THE CELL MEMBRANE, AND VARIOUS METABOLIC REACTIONS TAKE PLACE
THERE.
3.
HOUSING MANY SENSORY AND CHEMOTAXIS PROTEINS
4.
GENERATION OF CHEMICAL ENERGY
5.
CELL MOTILITY
6.
MEDIATION OF CHROMOSOMAL SEGREGATION DURING REPLICATION
• INWARD FOLDINGS OF THE CELL MEMBRANES— CALLED MESOSOMES—(CELLULAR RESPIRATION TAKES PLACE).
CHROMOSOME
• THE PROCARYOTIC CHROMOSOME IS A SINGLE, LONG,
SUPERCOILED, CIRCULAR DNA MOLECULE,
FUNCTION:
1.
SERVES AS THE CONTROL CENTER OF THE BACTERIAL CELL.
2.
CAPABLE OF DUPLICATING ITSELF, GUIDING CELL DIVISION, AND
DIRECTING CELLULAR ACTIVITIES.
• THE DNA-OCCUPIED SPACE WITHIN A BACTERIAL CELL IS SOMETIMES
REFERRED TO AS THE BACTERIAL NUCLEOID.
• SMALL, CIRCULAR MOLECULES OF DOUBLE-STRANDED DNA THAT ARE
NOT PART OF THE CHROMOSOME (REFERRED TO AS
EXTRACHROMOSOMAL DNA OR PLASMIDS)
CYTOPLASM
• IT IS SEMILIQUID
• CONSISTS OF WATER, ENZYMES,
DISSOLVED OXYGEN (IN SOME
BACTERIA), WASTE PRODUCTS,
ESSENTIAL NUTRIENTS, PROTEINS,
CARBOHYDRATES, AND LIPIDS
CYTOPLASMIC PARTICLES
• RIBOSOMES
• OFTEN OCCURRING IN CLUSTERS CALLED POLYRIBOSOMES OR
POLYSOMES .
• FUNCTION—THE SITES OF PROTEIN SYNTHESIS.
• A 70S PROCARYOTIC RIBOSOME IS COMPOSED OF A 30S
SUBUNIT AND A 50S SUBUNIT.
• CYTOPLASMIC GRANULES OCCUR IN CERTAIN SPECIES OF
BACTERIA. THESE MAY BE STAINED BY USING A SUITABLE STAIN,
AND THEN IDENTIFIED MICROSCOPICALLY. THE GRANULES MAY
CONSIST OF STARCH, LIPIDS, SULFUR, IRON, OR OTHER STORED
SUBSTANCES.
BACTERIAL CELL WALL
• FUNCTIONS—PROVIDING RIGIDITY, STRENGTH, PROTECTION AND DEFINES
THE SHAPE OF BACTERIAL CELL
• COMPOSED OF PEPTIDOGLYCAN (MUREIN), CONSISTING OF MANY
POLYSACCHARIDE CHAINS LINKED TOGETHER BY SMALL PEPTIDE
• GRAM-POSITIVE BACTERIA( EG: STAPHYLOCOCCUS) -THICK LAYER OF
PEPTIDOGLYCAN WITH TEICHOIC ACID AND LIPOTEICHOIC ACID MOLECULES.
• GRAM-NEGATIVE BACTERIA(EG: E.COLI) -MUCH THINNER LAYER OF
PEPTIDOGLYCAN, COVERED WITH A COMPLEX LAYER(OUTER MEMBRANE) OF
LIPID MACROMOLECULES
• MYCOPLASMA HAS NO CELL WALL
• SOME BACTERIA LOSE THEIR ABILITY TO PRODUCE CELL WALLS,
TRANSFORMING INTO TINY VARIANTS OF THE SAME SPECIES, REFERRED TO
AS L-FORM OR CELL WALL DEFICIENT (CWD) BACTERIA.
• SOME CWD BACTERIA ARE RESPONSIBLE FOR CHRONIC DISEASES SUCH AS
LYME DISEASE, RHEUMATOID ARTHRITIS, AND SARCOIDOSIS.
GLYCOCALYX (SLIME LAYERS AND CAPSULES
• GLYCOCALYX LOCATED OUTSIDE THEIR CELL WALL.
• SLIME LAYER, IS NOT HIGHLY ORGANIZED AND IS NOT FIRMLY ATTACHED TO THE CELL WALL.
EXAMPLE: PSEUDOMONAS PRODUCE A SLIME LAYER
• THE OTHER TYPE OF GLYCOCALYX, CALLED A CAPSULE( USUALLY A POLYSACCHARIDE), IS
HIGHLY ORGANIZED AND FIRMLY ATTACHED TO THE CELL WALL.
• EX; HAEMOPHILUS INFLUENZAE, KLEBSIELLA PNEUMONIAE, NEISSERIA MENINGITIDIS, AND
STREPTOCOCCUS PNEUMONIAE.
• NEGATIVE STAIN/INDIA INK STAINING:. OR . ANTIGEN–ANTIBODY TESTS ENCAPSULATED
BACTERIA -SMOOTH, MUCOID, AND GLISTENING COLONIES; THEY ARE REFERRED TO AS SCOLONIES. NONENCAPSULATED BACTERIA TEND TO GROW AS DRY, ROUGH COLONIES,
CALLED R-COLONIES.
• FUNCTIONS OF CAPSULE
1. VIRULENCE FACTOR
2. PROTECTION OF THE CELL WALL
3. IDENTIFICATION AND TYPING OF BACTERIA
MOTILITY ORGANELLES(FLAGELLA)
 FLAGELLA (SING. FLAGELLUM) ARE THREADLIKE, PROTEIN APPENDAGES
• FUNCTION: ENABLE BACTERIA TO MOVE.
• FLAGELLATED BACTERIA -MOTILE, NONFLAGELLATED BACTERIA -NONMOTILE.
• 10 TO 20 NM THICK; CANT BE SEEN WITH THE COMPOUND LIGHT MICROSCOPE.
1.
LOPHOTRICHOUS BACTERIA: TUFT OF FLAGELLA AT ONE END ,
2.
AMPHITRICHOUS BACTERIA.: ONE OR MORE FLAGELLA AT EACH END
3.
MONOTRICHOUS BACTERIA: A SINGLE POLAR FLAGELLUM
4.
PERITRICHOUS: SURROUNDING THE CELL
• A PROTEIN SUBUNIT CALLED FLAGELLIN IS PRESENT
• THE FLAGELLUM IS ATTACHED TO THE BACTERIAL CELL BODY BY A COMPLEX STRUCTURE
CONSISTING OF A HOOK AND A BASAL BODY.
• THE HOOK IS A SHORT CURVED STRUCTURE THAT APPEARS TO ACT AS THE UNIVERSAL
JOINT BETWEEN THE MOTOR IN THE BASAL STRUCTURE AND THE FLAGELLUM.
• THE BASAL BODY BEARS A SET OF RINGS, ONE PAIR IN GRAM-POSITIVE BACTERIA AND
TWO PAIRS IN GRAM-NEGATIVE BACTERIA.
FLAGELLA CONTN………….
PILI (FIMBRIAE)
• Pili (sing., pilus) or fimbriae (sing., fimbria) are
hair- like structures,
• most seen in Gram-negative bacteria.
• Composed of polymerized protein molecules
called pilin.
• Thinner than flagella, rigid structure, and are not
associated with motility.
• Functions: There are two types of pili:
1. one type enables bacteria to adhere or attach
to surfaces;
2. the other type (called a sex pilus) enables
transfer of genetic material from one bacterial
cell to another following attachment of the cells
to each other.
• PILIATED STRAINS CAUSE DISEASES LIKE URETHRITIS
AND CYSTITIS,
• NONPILIATED STRAINS OF THE SAME ORGANISMS
ARE UNABLE TO CAUSE THESE DISEASES
• GENETIC MATERIAL (USUALLY IN THE FORM OF A
PLASMID) IS THEN TRANSFERRED THROUGH THE
HOLLOW SEX PILUS FROM THE DONOR CELL TO
THE RECIPIENT CELL—A PROCESS KNOWN AS
CONJUGATION.
SPORES (ENDOSPORES)
• BACTERIA LIKE BACILLUS AND CLOSTRIDIUM FORM THICK-WALLED
SPORES AS A MEANS OF SURVIVAL WHEN THEIR MOISTURE OR NUTRIENT
SUPPLY IS LOW.
• BACTERIAL SPORES ARE REFERRED TO AS ENDOSPORES, AND THE PROCESS
BY WHICH THEY ARE FORMED IS CALLED SPORULATION.
• SPORES ARE RESISTANT TO HEAT, COLD, DRYING, AND MOST CHEMICALS.
• SPORES SURVIVE FOR MANY YEARS IN SOIL OR DUST, AND SOME ARE
QUITE RESISTANT TO DISINFECTANTS AND BOILING.
• GERMINATION OF A SPORE MAY BE COMPARED WITH GERMINATION OF
A SEED.
• SPORE FORMATION IS RELATED TO THE SURVIVAL OF THE BACTERIAL CELL,
NOT TO REPRODUCTION.
• ONLY ONE SPORE IS PRODUCED IN A BACTERIAL CELL AND IT GERMINATES
INTO ONLY ONE VEGETATIVE BACTERIUM
• USES OF SPORE:
1.
IMPORTANCE IN FOOD,INDUSTRIAL AND MEDICAL
MICROBIOLOGY
2.
STERILIZATION CONTROL
3.
RESEARCH
• DEMONSTRATION OF SPORE
1.
GRAM STAINING
2.
MODIFIED ZEIL NEELSON STAINING
CLASSIFICATION OF BACTERIA
CLASSIFICATION CAN BE DEFINED AS THE ARRANGEMENT OF ORGANISMS INTO TAXONOMIC
GROUPS (TAXA) ON THE BASIS OF SIMILARITIES OR RELATIONSHIPS.
NOMENCLATURE IS NAMING AN ORGANISM BY INTERNATIONAL RULES ACCORDING TO ITS
CHARACTERISTICS
IDENTIFICATION REFERS TO THE PRACTICAL USE OF A CLASSIFICATION SCHEME:
(1) TO ISOLATE AND DISTINGUISH DESIRABLE ORGANISMS FROM UNDESIRABLE ONES;
(2) TO VERIFY THE AUTHENTICITY OR SPECIAL PROPERTIES OF A CULTURE; OR, IN A CLINICAL
SETTING,
(3) TO ISOLATE AND IDENTIFY THE CAUSATIVE AGENT OF A DISEASE
CRITERIA FOR CLASSIFICATION OF BACTERIA
I.
MICROSCOPICALLY -CELL SHAPE ,PRESENCE OR ABSENCE OF SPECIALIZED STRUCTURES SUCH AS
SPORES OR FLAGELLA.
II.
STAINING PROCEDURES –GRAM STAINING(GRAM POSITIVE AND GRAM NEGATIVE)
III.
CHARACTERISTIC PIGMENTS-
IV. ON THE BASIS OF THEIR COMPLEMENT OF EXTRACELLULAR ENZYME(ZONES OF HEMOLYSIS IN AGAR
MEDIUM CONTAINING RED BLOOD CELLS)
V.
MEASUREMENT OF THEIR SENSITIVITY TO ANTIBIOTICS
PHYLOGENETIC CLASSIFICATIONS: TOWARD AN UNDERSTANDING OF EVOLUTIONARY RELATIONSHIPS AMONG BACTERIA
THANK YOU
SELF ASSESSMENT
1.
IMPORTANCE OF GLYCOCALYX IN PROKARYOTIC CELL IS
a.
PROTECTION AGAINST DESICCATION, ANTIBODIES AND VIRUSES
b.
HELPS IN DIGESTION
b.
HELPS IN REPRODUCTION
c.
HELPS IN MOTILITY
2. THE MOST COMMONLY ENCOUNTERED BACTERIA ARE ROUGHLY SPHERICAL. THE MICROBIOLOGICAL
TERM DESCRIBING THIS SHAPE IS
a.
COCCUS
b.
BACILLUS
c.
SPIRAL
d.
COMA
3. A BACILLUS BACTERIUM WITH A SINGLE FLAGELLUM AT EACH END IS DESCRIBED AS
a.
MONOTRICHOUS
b.
LOPHPOTRICHOUS
c.
AMPHITRICHOUS
d.
PERITRICHOUS
4. SHINY, STICKY COLONY OF STREPTOCOCCUS PNEUMONIAE IS LIKELY TO Be
a.
encapsulated and pathogenic
b.
.nonencapsulated and nonpathogenic
c.
nonencapsulated and pathogenic
a.
encapsulated and nonpathogenic
5. DIFFERENCES BETWEEN EUKARYOTIC AND PROKARYOTIC CELLS INCLUDE ALL OF THE FOLLOWING EXCEPT
a.
EUKARYOTIC CELLS HAVE MITOCHONDRIA
b.
PROKARYOTIC CELLS HAVE MORE COMPLEX CELL WALLS
c.
EUKARYOTIC CELLS HAVE CILIA AND FLAGELLA WITH COMPLEX STRUCTURE
d.
PROKARYOTIC CELLS HAVE NO GENETIC MATERIAL
WRITE SHORT ESSAYS ON THE FOLLOWING
1.
SPORES
2.
FUNCTIONS OF A CAPSULE
3.
CELL WALL
4.
WRITE 2 EXAMPLES OF EACH GRAM POSITIVE AND GRAM NEGATIVE BACILLI AND COCCI
5.
WHAT ARE THE DIFFERENT METHODS TO CLASSIFY BACTERIA
DRAW DIAGRAM OF A FLAGELLA