BACTERIAL MORPHOLOGY- MICROPARA

28問 • 11ヶ月前

問題一覧

• Prokaryotic • have simpler structures compared to eukaryotic organisms. • may be classified into three basic shapes: - coccus (pl. cocci) - bacillus (pl. bacilli) - spiral shaped or curved

BACTERIA

SHAPES • spherical or round shaped organisms (e.g., Staphylococcus,Streptococcus)

COCCI

SHAPES • Rod shaped organisms • e.g., Escherichia coli, Salmonella • Some may be very short, resembling elongated cocci called coccobacilli (e.g., Haemophilus influenzae)

BACILLI

SHAPES may show variations in their morphology

SPIRAL

envelope serves to protect the bacteria from harsh environmental conditions.

ENVELOPE STRUCTURES

• outermost covering of some bacteria • It is a gelatinous substance that is located external to the cell wall • composed of polysaccharide or polypeptide, or both.

GLYCOCALYX

GLYCOCALYX if it is strongly attached to the cell wall

CAPSULE

GLYCOCALYX if it is loosely attached

SLIME LAYER

• sometimes called the murein sacculus • Its principal component is PEPTIDOGLYCAN • It is MULTI LAYERED in GRAM POSITIVE bacteria • SINGLE LAYERED in GRAM NEGATIVE bacteria Functions: • provides rigid support • gives shape to the bacteria • It protects the bacteria from osmotic damage • plays an important role in cell division

CELL WALL

Special components of gram positive cell wall • comprise major surface antigens of gram positive organisms • can elicit antibody response Functions: • for the attachment of the organism to the host cell (In some gram positive organisms such as Staphylococcus aureus) • provide tensile strength to gram positive bacterial cell walls.

TEICHOIC ACIDS

Special components of gram positive cell wall • include neutral sugars • mannose, arabinose, rhamnose,and glucosamine • It also includes some acidic sugars • glucuronic acid • mannuronic acid

POLYSACCHARIDES

Special components of gram negative cell walls • BI LAYERED structure where the inner leaflet is composed of a LIPOPOLYSACCHARIDES (LPS). • It has special protein channels • allow the PASSAGE of small or low molecular weight hydrophilic substances • such as sugars and amino acids. • LPS has a complex glycolipid called LIPID A • responsible for its endotoxin activity • It is located in the outer leaflet of the outer membrane. • The inner core is a polysaccharide made up of REPEAT UNITS. • This repeat unit is also called the O ANTIGEN • which is unique for every species of bacteria

OUTER MEMBRANE

Special components of gram negative cell walls • to anchor the outer membrane to the peptidoglycan layer • stabilizes the outer membrane

LIPOPROTEIN

Special components of gram negative cell walls • a fluid filled space between the outer membrane and the inner plasma membrane. Contains: • enzymes for the breakdown of large non transportable molecules into transportable ones • enzymes that serve to detoxify and inactivate antibiotics

PERIPLASMIC SPACE

Special components of gram negative cell walls • acid fast organisms - Mycobacterium tuberculosis • possess an outer layer that is LIPID RICH • cell wall is composed of large amounts of waxes that are known as MYCOLIC ACID • inner layer of the cell wall • is also made up of peptidoglycan but because the outermost layer is lipid rich, cell walls of acid fast organisms are HYDROPHOBIC. • reason why they CANNOT BE STAINED using the reagents used in gram staining. • The hydrophobic nature of their cell wall protects them from harsh chemicals • such as strong acids and detergents.

ACID FAST CELL WALL

PROJECTING STRUCTURES • thread like structures • made up entirely of molecules of the protein sub unit flagellin. • They project from the capsule • organs for motility

FLAGELLA

4 TYPES OF FLAGELLA - single polar flagellum

MONOTRICHOUS

4 TYPES OF FLAGELLA - A tuft of flagella at one end of the bacterium

LOPHOTRICHOUS BACTERIFELLA

4 TYPES OF FLAGELLA flagella at both ends of the bacterium

AMPHITRICHOUS

4 TYPES OF FLAGELLA flagella all around the bacterium

PERITRICHOUS

PROJECTING STRUCTURES • rigid surface appendages found on many gram negative bacterial • fine and short in comparison with flagella • Their structural protein sub units are called pilins FUNCTIONS: • may also function for motility • for adherence to cell surface (common pili) • attachment to another bacterium during a form of bacterial gene exchange called conjugation (sex pili)

PILI

PROJECTING STRUCTURES • are also called endoflagella • found in spirochetes(e.g., Treponema pallidum causing syphilis) • composed of bundles of fibrils, the structures of which are similar to flagella. • They arise from the ends of the bacterial cell and spiral around the cell. • The filaments rotate producing movement of the outer sheath of the spirochetes propelling them forward

AXIAL FILAMENTS

PROJECTING STRUCTURES • Located beneath the cell wall • sometimes called the cell sac • because it encloses the cytoplasm of the cell. • is a selectively permeable membrane • allows for transport of selected solutes. • In aerobic organisms • the site of the electron transport chain • serves as the site of ATP production. • It therefore serves the function of the mitochondria, which are not found in prokaryotic cells. • contains the enzymes needed for the biosynthesis of DNA, cell wall components, and membrane lipids

CYTOPLASMIC MEMBRANE

INTERNAL STRUCTURE • Bacteria have no true nucleus that is surrounded by a nuclear membrane • Bacteria possess a single, circular, double stranded DNA

NUCLEIOD

INTERNAL STRUCTURE • functions for cell division • It is also involved in the secretion of substances Produced by bacteria

MESOSOMES

INTERNAL STRUCTURE • function for protein synthesis. • Unlike eukaryotic ribosomes, bacterial ribosome is smaller (70S).

RIBOSOMES

INTERNAL STRUCTURE • found in certain bacteria • serve for storage of food and energy (e.g., metachromatic granules of Corynebacterium diphtheriae or Much granules of Mycobacterium tuberculosis)

GRANULES

INTERNAL STRUCTURE • structures produced by many bacteria when they are placed in a hostile environment • composed of dipicolinic acid • confers resistance to heat, drying, chemical agents, and radiation • making it very difficult to destroy • The process of spore production is called sporulation • occurs when the environmental conditions are detrimental to the bacteria • When environmental conditions become favorable ▪It revert to their vegetative state through a process called GERMINATION • Some gram positive, but never gram negative, bacteria form

ENDOSPORES

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