Collage of Basic Science and Hummanities Submitted to : Dr. Anurag Yadav Asst. Prof. of Microbiology Submitted by : Lalpara Ajay Kumar A. 6th sem. Microbiology Reg.No :12-00053-2012 Roll No. : 15 Seminar Topic: Anatomy and Physiology of prokaryotic cell i

Anatomy And Physiology of Prokaryotic Cell

Bacterial Shapes, Arrangements, and Sizes Vary in shape, size, and arrangement but typically described by one of three basic shapes: Coccus – spherical Bacillus – rod Coccobacillus – very short and plump Vibrio – gently curved Spirillum – helical, comma, twisted rod, Spirochete – spring-like 3 3

Bacterial Shape and Arrangement

Bacterial Arrangements Arrangement of cells is dependent on pattern of division and how cells remain attached after division: Cocci: Singles Diplococci – in pairs Tetrads – groups of four Irregular clusters Chains Cubical packets (sarcina) Bacilli: Diplobacilli Palisades 5 5

Arrangement of bacilli

Prokaryotic Cell Structure

Cytoplasmic Membrane Surrounds cytoplasm and defines boundaries of cell Acts as barrier, but also functions as an effective and highly discriminating conduit between cell and surroundings Made up of phospholipid bilayer

Movement of Molecules through Cytoplasmic Membrane Several ways for molecules to move through membrane Simple Diffusion Osmosis Facilitated Diffusion Active Transport

Simple Diffusion Does not require expenditure of energy Process by which some molecules move freely into and out of the cell Small molecules such as carbon dioxide and oxygen

Transport Proteins Transport proteins (or transporters) responsible for: Facilitated Diffusion Active Transport

Cell Wall Composed of peptidoglycan Comprised of alternating NAG and NAM molecules Attached to each NAM is four amino acid peptide: tetrapeptide

Categories of Bacteria Two Major Categories: Difference due to difference in chemical structures of their cell walls Gram positive: stains purple Gram negative: stains red

Gram-Positive Cell Wall Thick, homogeneous sheath of peptidoglycan 20-80 nm thick Includes teichoic acid and lipoteichoic acid: function in cell wall maintenance and enlargement during cell division; move cations across the cell envelope; stimulate a specific immune response Some cells have a periplasmic space, between the cell membrane and cell wall

Gram-Negative Cell Wall Composed of an outer membrane and a thin peptidoglycan layer Outer membrane is similar to cell membrane bilayer structure Outermost layer contains lipopolysaccharides and lipoproteins (LPS) Lipid portion (endotoxin) may become toxic when released during infections May function as receptors and blocking immune response Contain porin proteins in upper layer – regulate molecules entering and leaving cell Bottom layer is a thin sheet of peptidoglycan Periplasmic space above and below peptidoglycan 16 16

Outer Membrane Unlike any other membrane in nature A lipid bilayer with the outside layer made of lipopolysaccharides instead of phospholipids Also called LPS Contains Porins

Periplasm - Region between cytoplasmic membrane and the outer membrane - Gel-like fluid Filled with secreted proteins and enzymes

External Structures Flagella Axial Filaments Fimbrae and Pili

Filamentous Protein Appendages Anchored in membrane and protrude from surface Flagella: long structure responsible for motility Fimbrae and Pili: shorter, responsible for attachment

Fimbriae Fine, proteinaceous, hairlike bristles emerging from the cell surface Function in adhesion to other cells and surfaces

Pili Rigid tubular structure made of pilin protein Found only in gram-negative cells Function to join bacterial cells for partial DNA transfer called conjugation

Four types of bacteria with flagella Montrichious- one flagella Amphitrichous- flagella at both ends Lophitrichous- many flagella at the end of the cell Peritrichous- flagella all over entire cell

Axial Filament Present in Spirochetes Attach at end of cell, spiral around, underneath an outer sheath Move like a corkscrew

Internal Structures of Prokaryotic Cells

Cytoplasm Substance of cell inside the cytoplasmic membrane About 80% water Thick, aqueous, semitransparent, elastic

Chromosome Found within a central location known as nucleoid Single, circular, double stranded Consists of all DNA required by cell

Plasmids Small circular, double-stranded DNA Free or integrated into the chromosome Duplicated and passed on to offspring Not essential to bacterial growth and metabolism May encode antibiotic resistance, tolerance to toxic metals, enzymes, and toxins Used in genetic engineering - readily manipulated and transferred from cell to cell 29 29

Ribosomes Made of 60% ribosomal RNA and 40% protein Consist of two subunits: large and small Prokaryotic differ from eukaryotic ribosomes in size and number of proteins Site of protein synthesis 30 30

Endospores Occurs in members of genera Bacillus and Clostridium Dormant cell produced by a process called Sporulation Germination- when they exit the dormant state and then become a vegetative cell Several species of endospore formers can cause disease