MICROBES (Viruses & Bacteria)

Transcription

1 MICROBES (Viruses & Bacteria) I. VIRUSES A. General Characteristics f Viruses - Viruses are infectius agents with bth living and nnliving characteristics. - They can infect animals, plants, and even ther micrrganisms. 1. Living characteristics f viruses a. They reprduce at a fantastic rate, but nly in living hst cells. b. They can mutate. 2. Nnliving characteristics f viruses a. They are acellular, that is, they cntain n cytplasm r cellular rganelles. b. They carry ut n metablism n their wn and must replicate using the hst cell's metablic machinery. * In ther wrds, viruses dn't grw and divide. Instead, new viral cmpnents are made and assembled within the infected hst cell. c. They pssess DNA r RNA but never bth. 3. Criteria used t define a virus a. They cntain nly ne type f nucleic acid: DNA r RNA, but nt bth. b. They are ttally dependent n a hst cell fr replicatin. (They are strict intracellular parasites.) c. Viral cmpnents must assemble int cmplete viruses (virins) t g frm ne hst cell t anther. B. Structure 1. DNA r RNA cre enclsed in a prtein cat (capsid) - genetic material nly cdes fr making cpies f the virus 2. May have a viral envelpe cnsisting f phsphlipids arund the capsid 3. N nucleus, cytplasm, r membranes 4. smaller than a bacterial cell C. Functin 1. bligate intracellular parasites (require a hst cell t reprduce) 2. d nt carry ut cellular fxns (i.e. respiratin) 3. d nt generate metablic activity 4. bacteriphage virus that infects bacteria T1-T7 are bacteriphages that infect the cmmn intestinal bacterium Escherichia cli (E. cli) 5. mycphage - infect nly fungi D. Replicatin 1. befre a virus can enter and reprduce in a cell, it has t recgnize and attach t a specific receptr site n the plasma membrane f the hst cell. 2. prteins n the surface f each virus has a 3-D shape that matches the shape f a mlecule in the plasma membrane f its hst cell. 3. nce attached t the plasma membrane, the virus has t get inside the cell and take ver the cell s metablism.

2 Lytic Cycle 4. LYTIC CYCLE hst cell is destryed - ATTACHMENT (b) Attach t a hst cell - ENTRY (c) insert genetic material - REPLICATION (d) Destry hst cell DNA/make new virus particles - ASSEMBLY (e) Assemble new virus particles int new viruses - LYSIS and RELEASE (f) Burst hst cell t release virus - Attach t new hst cell (a)

3 5. LYSOGENIC CYCLE hst cell is nt immediately destryed, viral DNA becmes part f hst cell s DNA - ATTACH - attach t a hst cell - ENTRY - insert genetic material - INTEGRATION - Viral DNA becmes part f hst s genetic makeup (prphage- des nt interfere with nrmal functining f a hst cell) - REPRODUCTION - Viral DNA is reprduced each time the cell divides - EXIT - prphage pps ut f the hst cell s DNA - reasns fr prphage ppping ut is unknwn - LYTIC CYCLE - Enter int Lytic Cycle (attachment, entry, replicatin, assembly, lyses and release) 6. Diseases a. Cld Sres/Herpes Simplex 1 (Lysgenic cycle) - when virus pps ut, yu get anther cld sre b. HIV (Retrvirus) - wrks by prducing a small # f viruses each time it reprduces - as lng as cells are prducing nly a small # f viruses, the persn (hst) may nt shw symptms fr sme time - this shws why mst peple wh have HIV develp AIDS - as mre cells becme infected and the viruses enter the lytic cycle, the WBCs are killed - eventually the bdy s immune system breaks dwn and can n lnger fight ff disease

4 Kingdm Mnera: The Prkarytes - Mst numerus and widespread rganisms - Only kingdm f prkarytic rganisms - Have a cell wall f peptidglycan - structural mlecule nt fund in eukarytes ARCHAEBACTERIA - Mst ancient f all living things - 3 types 1. Thermacidphiles - extremely ht and acidic water - mist areas in and arund sulfur ht springs - die f cld at temps f 55 C (131 F) 2. Methangens - bligate anaerbes (free Oxygen kills them) - 10 knwn species - use CO2 t prduce methane (CH4) as waste - exist in diverse envirnments - frm scalding vlcanic deep-sea vents t intestines f mammals *this is why yu can light a puff f flatulence!* 3. Halphiles - extremely salty cnditins - pink pigments = cnspicuus in large cncentratins - Dead Sea and Great Salt Lake EUBACTERIA Mrphlgy - shape, size, appearance - lack membrane-bund nuclei - DNA frms a lped-tangle ( nucleid ), but n membrane surrunds it - cntain plasmids (small lps f DNA) can be transmitted frm ne bacteria t anther - transmitted thrugh cnjugatin ( sex ) r viruses - makes bacteria amazingly adaptable - beneficial genes (such as thse fr antibitic resistance) may spread rapidly thrugh a bacterial pp. - N membrane-bund rganelles (i.e. mitchndria r chlrplasts) - phtsynthetic bacteria ( cyanbacteria ) may be filled with tightly packed inner flds f the uter membrane. - increases ptential surface area fr phtsynthesis - Cell membrane surrunded by a cell wall - *except in ne grup = mllicutes/mycplasmas - cmpsitin f cell wall varies - is an imprtant tl fr identificatin and classificatin Shapes - imprtant identificatin and classificatin tl - 3 basic types 1. Bacilli (singular = bacillus) - rd-shaped - mst cmmn - Escherichia cli that lives in yur intestines - Lactbacillus spp. (agents f tth decay, ingredient in ygurt) - Bacillus anthracis (causes anthrax in sheep, cattle and humans) 2. Ccci (singular = cccus) - spherical - very cmmn - Streptcccus spp. (strep thrat in humans) - strept = chain

5 - Staphylcccus spp. (gangrene in untreated wunds) - staphyl = cluster 3. Spirilla (singular = spirillum) - spiral-shaped - largest in size - easiest t identify Gram Staining - develped by Danish physician Hans Christian Gram in mst widespread methds f bacterial classificatin - identifies cntent f bacterial cell wall Gram Stain Prcedure 1. Fix smear f bacteria t a slide 2. (Primary stain) Fld slide with Crystal Vilet fr 10 secnds (wash with water) 3. (Mrdant) Fld with Gram s Idine fr 10 secnds (wash with water) 4. (Declrizer) Declrize with 95% ethanl (wash with water) 5. (Secndary Stain) Fld with Safranin (pink) fr 10 secnds (wash with water) 6. Air dry 7. Fcus under light micrscpe t view utcme f bacterial appearance - 2 types f cell walls 1. Gram Negative Bacteria (G-) - appear bright pink t red after the staining prcedure - have a secnd membrane surrunding the cell wall made up f lypplysaccharides (LPS) - Crystal Vilet dye cannt penetrate the LPS layer, it s rinsed ut with the alchl - 75% f knwn bacteria are G- - include rickettsias, chlamydias, and phtsynthetic bacteria 2. Gram Psitive Bacteria (G+) - appear purple t brwn after the staining prcedure - have a membrane rich in peptidglycan which attracts the Crystal Vilet dye - N LPS layer - all rd-shaped bacteria are G+ - Cell wall characteristics are related t disease-causing ptential - effective way t fight bacteria is by interfering with cell wall frmatin - b/c eukarytic cell walls and membranes dn t have a similar chemical makeup, the medicines used have n effect n the eukarytic (plant r animal) cells Lcmtin - squirm, glide, prpulsin - flagella is different frm thse in a eukarytic cell - cmpsed f a prtein ( flagellin ) nt fund in eukarytes - rtates t prpel rganism instead f whip-like as in eukarytes Reprductin - Cnjugatin - frm f sexual reprductin - swapping genetic infrmatin - Binary Fissin - mst bacteria reprduce this way - d nt g thrugh mitsis b/c f DNA structure 1. circular DNA mlecule is replicated 2. then the cell splits int tw identical cells each cntaining an exact cpy f the riginal cell's DNA. MYCOPLASMAS - smallest living things ever discvered - have the MIN amt. f DNA needed fr a fxnal cell - d nt have cell wall characteristics f ther bacterial types

6 - intracellular plant r animal parasites - prtects them frm changes in envirnmental and water pressures - Penicillin (kills mst ther bacteria by interfering with cell wall fxning) des nt wrk against Mycplasmas b/c they have n cell wall Bacteria and Humans Human micrbita (r "flra"): micrbial inhabitants f the human hst apprx half f the cells f a human are bacterial cells Resident micrbita - the cllectin f bacteria that frm stable symbitic relatinships with us are called the Transient micrbita - bacteria just passing thrugh - includes the Opprtunistic pathgens(cause disease if given a chance) 2. Where des the micrbita cme frm? fetus is sterile (r nearly sterile) -it is thught that the newbrn picks up sme bugs in the birth canal, mst thers in the hspital newbrn micrbita resembles that f a sick adult in many ways by tw years f age, the micrbita matures t clsely resemble the adult ecsystem 3. What is the resident micrbita gd fr? the general term fr the assciatin between micrbes and us is symbisis mutualism - bth we and micrbes benefit frm the symbisis cmmensalism - the micrbe benefits withut helping r harming us parasitism - the micrbe benefits, and harms us in the prcess examples f mutualism immunprtectin: prviding antigens that will help us ward ff later infectins prviding vitamins cmmensalism can becme parasitism due t changes in lcatin 4. Where the micrbita is (and isn't) bacteria are nt fund (in healthy humans) in the bld: if bacteria are there, we call it bacteremia r bld pisning cerebrspinal fluid (tissue surrunding the brain and spinal chrd): meningitis is the name f this infectin tissues lungs-pneumnia heart-endcarditis brain-encephalitis Where bacteria are (basically, every expsed area f ur bdies) skin nasal area eyes and ears alimentary canal (muth t anus) and geniturinary tract 5. What we d t keep ut transients the nature f the mucsal surface