Microbiology sheet ()

Transcription

1 Microbiology sheet () Made by : Majd abu-fares corrected by : Abd. salman

2 Note: (slide "18" min: "6:15-9:50") DATE : Acid-fast Cell Walls Means: bacteria that don't pigment to gram stain Acid-fast = resistance to acid Ex: Pulmonary Tuberculosis ( TB-Bacilli) Genus Mycobacterium and Nocardia Mycolic acid (waxy lipid) covers thin peptidoglycan layer *This layer is external to cell wall *It covers the thin peptidoglycan layer *It is the reason why this kind don't pigment to gram stain (the stain is not instructed by the bacteria) Do not stain well with Gram stain use acid-fast stain *We use H2SO4 /HCL (acid fast stain " strong acids") * It's color =Orange Red Note: (slide"19" min: "9:51-14:30") Bacteria with No Cell Wall: Mycoplasmas Mycoplasm: no cell wall ( less cell wall )* *Mycobacteria : acid-fast ( genus includes pathogens known to cause serious diseases in mammals " myco= fungus") less cell wall = no cell wall = without * * The smallest bacteria type *most of it are pleomorohic (can change its shape easily) Instead, have cell membrane which incorporates cholesterol compounds (sterols), similar to eukaryotic cells * This give it the rigidity Cannot be detected by typical light microscopy *Can't see under LM Note ( slide"20" min: "14:37-15:58")

3 Cell Wall Biochemistry What is peptidoglycan? 2 units : 1- N-acetylglucosomine 2-N- acetylmuraic acid Types of polypeptide chains in the peptidoglycan : 1) tetrapeptide - side chain (Vertical) 2) peptide - cross bridge (Horizontal) *Penicillin break-down the peptide cross-bridge so the bacteria become less cell wall يعمل البنسلين على تكسير الروابط االفقيه "خماسيه و سداسيه" فتتكسر جدار الخليه" 1) Note ( slide "21" min: 16:18-24:14") Structures External to the Cell Wall Glycocalyx: means sugar coating; often polysaccharide or polypeptide layer external to the cell wall. Capsules: organized, consolidated, well attached. *Present in uniform way *Encapsulated= capsuled bacteria = bacteria with capsule * More pathogenic ( inhibit the process of phagocytosis) * Not necessarily the whole bacteria to be pathogeinc it might be a part of it *Staining process is attraction process * We use india-ink or eyosin (red) فتبدو بدون لون capsule سالبه تنصبغ البكتيريا من الداخل دون صبغ capsule *لما تكون الصبغه سالبه و ال تنصبغ capsule يعني colorless *The cause of meningitis ( )السحايا is type B capsule. We must give children vaccins. Slime Layer: unorganized; loose; removed easily.

4 Function in attachment; protection; virulence. *لحدوث المرض يجب ارتباط البكتيريا بالخليه بشكل كامل مثل االمعاء اذا لم تكن البكتيريا مرتبطه باالمعاء ممكن من حركه االمعاء التموجيه ان تفلت فال يحدث المرض 2) S-layer: extremely well organized layer of protein or glycoprotein subunits that forms a rigid mesh, next to cell wall. *Polysaccharide + protein > to classification * S-layer / Glycocalyx = in function difference in structure Functions in -adherence - Protect the bacteria from enzyme and change in Ph - Contribute to virulence (antiphagocytosis, anticomplements) (عامل من العوامل االمراضيه ( *Virulence *complements: proteins exist in serum that complete the immune process. Note ( slide "22" min: "24:37-34:25") Structures External to the Cell Wall Fimbriae : (pili) 1000 s of thin (~5 nm) & short appendages of helical proteins. Attachment to (specific) surfaces. * Short *Straight Sex Pili: *Pilli : 1) common "fimbriae" 2) sex " negative gram only " "transfer the genetic material " * Piliin (protein of pili)

5 1-10 slightly larger than fimbriae. Only in cells with a fertility plasmid (F factor), called donors. * F factor = plasmid =fartility = donor Attaches to like cells without F factor, called recipients. Facilitates genetic transfer between cells; with recipient gaining the F factor and possibly other genes. plasmid F+ donor cell ( male) ( conjugation=like bridge) F- = recipient ( female) (by sex pili) *After conjugation process the " F-" become " F+" * conjugation هي عملية اقتران متزاوج *After replication a copy move from the + to - Flagella: Mostly made of flagellin. Filament thick (20 nm) & long (10-20 µm). *Longer *Thicker *Zigzag ( not totally straight )

6 Varied locations on cell a) Peritrichous ( more dangerous/ more spread /more problems) b ) Monotrichous ( single ) c) Lophotrichous ( a group on one side ) d) Amphitrichous e) Atrichous ( without ) Note ( slide "24" min : "24:53-33:48) Structure of flagellum : 1- Filament 2-Hook 3- Basal body

7 * It differ from gram positive or negative * Gram Positive : 2 rings in the plasma membrane * Gram Negative : 4 rings " 2 in Cell wall (includes peptidoglycan and outer membrane) - 2 in plasma membrane " Note ( slide "25" min 33:52-42:13") Endospore Formation )ابواغ داخليه ) *Endospore *More pathogenic than other bacteria why? because it is resistance to environment conditions #Dr Q: Is it the spore formation of the bacteria need to reproduction? #Answer: No #DR Q: why? النه spore ينتج من ) cell vagetative cell ( mother تحت ظروف غير طبيعيهsporulation و يمكن ان يعود الى there is no increase in number يعني تعرض لظروف مناسبهgermination vagetativeاذا cell * ال يمكن للخليه انتاج spores اال اذا كانت تحمل ذلك في جيناتها يعني *Cell can product spore genetically only

8 Dormant, tough, non-reproductive structure germination vegetative cells * Germination: spore become a vegetative cell again Spore forming genera: Clostridium (very dangerous bacteria) Resistance to UV and radiation, desiccation, lysozyme, temperature, starvation, and chemical disinfectants Relationship to disease Sporulation: Endospore formation حاله السكون او الثبات = stage * Dormant * Sporulation : the vegetative cell ( mother ) disappear, spore only exist but before that the DNA replication then a copy of it move to the spore, the spore have a copy of the DNA of the mother cell so it can stay at doorment stage ( save bacteria from extinction) Germination: Return to vegetative state * Spore can stay 100,000 years so we use it as biological weapon * Very dangerous * Classified according to the site of the spore location: 1- Central 2- Terminal 3- Sub-terminal Note ( slide "26" min: " 42:15-44:33") )ابواغ اوليه ) Forespore #2#: * 2 Plasma membrane between them > peptidoglycan * The spore coat Form ( outer )

9 Note ( slide "27" min:"44:33-25:15") Depending on the species, the endospore might be located terminally (at one end), subtermillally (near one end, or celltrally inside the vegetative cell. When the endospore matures, the vegetative cell wall ruptures (lyses), killing the cell, and the endospore is freed. Most of the water present in the forespore cytoplasm is eliminated by the time sporulation is complete, and endospores do not carry out metabolic reactions. * No metabolic-activity why? because there is no water inside the spore ( dormant stage ) Note ( slide "28" min:"45:16-48:50")

10 The highly dehydrated endospore core contains only DNA, small amounts of RNA, ribosomes, enzymes, and a few important small molecules. The latter include a large amount of an organic acid called dipicolillic acid which is accompanied by a large number of calcium ions. *Because of dipicolillic acid and calcium ions it doesn't pigment ) ينصبغ unless )ال we increase the temperature Endospores can remain dormant for thousands of years. An endospore returns to its vegetative state by a process called Germination. Sporulation in bacteria is not a means of reproduction. This process does not increase the number of cells. vegetative cell mother cell spore Sporulation Germination spore