Microbiology Unit 1 PDF

Welcome to microbiology World of microorganisms/human disease Vast majority of microbes are beneficial Five groups of medically important microbes: – Viruses – Bacteria (Kingdom Eubacteria) – Fungi (Kingdom Fungi) – Protozoans (Kingdom Protista) – MCAPS: (Kingdom Animalia)...

Welcome to microbiology World of microorganisms/human disease Vast majority of microbes are beneficial Five groups of medically important microbes: – Viruses – Bacteria (Kingdom Eubacteria) – Fungi (Kingdom Fungi) – Protozoans (Kingdom Protista) – MCAPS: (Kingdom Animalia) multicellular animal parasites also known as (aka) helminths See Section 1.2 in the eText for more information  Three Domains v. Six Kingdoms Biologists put living things in different groups based on their fundamental characteristics The Three Domain System is widely used The Six Kingdom system is easier to use Use the diagram above to help you place the five groups of medically important microbes in the correct Domains and Kingdoms Viruses have no kingdom; they are non-living  Scientific names [Reading: page 4] All known living things have a two-part name that is their scientific name or species name Homo sapiens for humans; Canis familiaris for dogs; E. coli is short for Escherichia coli The first part is the genus name and the second part is the specific epithet eText Section 1.2 gives more information and the rules for writing scientific names correctly  Viruses and bacteria Viruses and bacteria will be our main focus – Most diseases in the developed (industrialized) world are caused by either bacteria or viruses – The developing (non-industrialized) world has more protozoan & helminthic diseases than the developed world; this is mainly due to sanitation Developed world: US, Europe, Japan Developing world: Africa, Asia Thousands of small, round bacterial cells. (1,000 X) Large, rod-shaped bacteria (1,000 X) A virus particle (500,000 X)  History of microbiology: very old 1665Robert Hooke saw cells!!! 1673Anton van Leeuwenhoek saw microbes (they were cells, too) 1735Linnaeus developed system for naming living organisms 1798Edward Jenner made and used a smallpox vaccine  History of microbiology, old Louis Pasteur—mid 1800s – Disproved spontaneous generation – Made rabies and fowl cholera vaccines – Developed aseptic techniques – Showed fermentation was biological process Robert Koch—also mid 1800s – Germ theory of disease widely accepted – Culturing (growing) and staining of MO for microscopes was advanced and standardized  History of microbiology, newer 1930Sir Alexander Fleming discovers penicillin; sulfa drugs were made 1930Wendell Stanley described the structure of a virus; showed this virus was made of RNA & protein 1930The first transmission electron microscope was made; biologists could see virus particles History of microbiology, newest 1950Watson and Crick announce the discovery of the structure of DNA 1960Sabin poliovirus vaccine was made and used; contains active, but weakened poliovirus (OPV) 1985HIV identified and named  Light and electron microscopes The compound light microscope (CLM) and the transmission electron microscope (TEM) are the most important in microbiology CLMs are used in college biology labs and diagnostic labs; magnify images1000 X; used to observe bacteria, blood, tissues and more TEMs are research tools; magnify images up to 10,000,000 X; used to observe viruses, ribosomes, and other extremely small things  Viruses and virus structure Viruses are acellular, non-living entities Viruses are submicroscopic, meaning they are too small to see with a light microscope Viruses made of nucleic acid (DNA or RNA) that is enclosed within a protective shell Viruses cannot multiply (reproduce) on own; they reproduce only inside host cells Rabies virus, smallpox virus, influenza virus TEM of human adenovirus 5 (magnification ~500,000 X) TEM of tobacco mosaic virus (magnification ~1,500,000 X) An RNA molecule (TMV genome) is inside the hollow cylinder (TMV capsid).  Bacteria and bacterial structure Bacteria are cellular, living entities Bacteria can multiply on their own, but there are a few exceptions to this statement Bacterial cells are prokaryotic (prokaryotes) Bacteria have cell wall, plasma membrane, cytoplasm, ribosomes, DNA and RNA, more Streptococcus pyogenes (strep throat), Escherichia coli (intestinal bacteria) Images in color: bacterial cells seen with CLM (magnified 1,000 X) Black and white images: bacterial cells see with SEM (magnified ~10,000 X)  Fungi Made of eukaryotic cells (eukaryotes) Some fungi, the yeasts, are unicellular; other fungi known as molds are multicellular Cause relatively few diseases in animals Ringworm, diaper rash, athlete’s foot Candida albicans is a yeast and causes a common infection known as candidiasis  Protozoans Protozoans are eukaryotic organisms Most (if not all) protozoans are unicellular Protozoans are “animal-like” – Most move around and ingest food Disease-causing protozoans are called parasites, or said to be parasitic Malaria, sleeping sickness, and amoebic dysentery are caused by protozoans  MCAPS or helminths MCAPs are multicellular, eukaryotic animals MCAPs are not always microscopic, but they are still part of microbiology Like protozoans, MCAPs are called parasites There are three kinds of MCAPs: – Tapeworms, round worms, flukes MCAPs are also known as (aka) helminths  Basic types of cells [Reading: pages 73 and 96] All cells either prokaryotic or eukaryotic – Prokaryotes: bacteria (Bacteria & Archaea) – Eukaryotes: all cells except bacteria (Eukarya); includes protozoans, fungi, and animals Genetic material (DNA) arranged differently – Eukaryotic cells have DNA in the nucleus, which is separated from the cytoplasm by a membrane – Prokaryotic cells have a nucleoid region instead of a nucleus; the bacterial DNA (chromosome) is in direct contact with the cytoplasm  Basic types of cells (continued) Presence of membrane-bound organelles – Eukaryotes have many membrane-bound organelles, like mitochondria, the nucleus, endoplasmic reticulum, and vacuoles – Prokaryotes do not have membrane-bound organelles; the cell is not compartmentalized Unicellular or multicellular – Eukaryotes can be unicellular or multicellular – All prokaryotes are unicellular Page 73 and also Table 4.2 page 96  Virus reproduction Reproduction occurs only in infected cells – Animal viruses “trick” the cell into taking it in – The virus uses cell’s workings to copy its nucleic acid and make the parts for protective shell – New virus particles leave the cell: 1) when the cell dies and breaks apart, or 2) when the living cell is “tricked” into releasing the virus particles – Released virus particles drift and/or are carried to new host cell and the infection cycle repeats See page 379  Bacterial reproduction Nearly all bacteria can reproduce on own Require suitable environment to reproduce Cells simply divide; called binary fission – Cells absorb nutrients from surroundings – They use the nutrients to “build up” the cell – Duplicate their DNA; DNA molecules separated – Divide cell in two; new cells can repeat process Most disease-causing bacteria multiply in the spaces between host cells, not inside the cells See page 165  Fungal reproduction Fungi can reproduce on their own Require suitable environment – Food, water, proper temperature, etc. Yeasts and molds reproduce differently – Yeasts can reproduce by budding and/or by ordinary eukaryotic cell division – Molds form spores, reproductive cells that can grow into a new organism; spores can resist drying out; most mold spores are air-borne fungal spores being released  Protozoan reproduction Are truly living organisms, but are usually unable to reproduce outside their host(s) Require host to provide suitable environment Have complex nutritional and environmental needs that are only met by a host organism Often have life cycles with more than one host and many different stages or “forms” Malaria & amoebic dysentery are examples  Plasmodium (a protozoan) The microorganism that causes malaria Its complex life cycle summarized: – Sporozoites mosquito→ human – Merozoites human / in liver and blood – Gametocytes human → mosquito – Sporozoites mosquito → human again Mosquito called vector; it transmits illness Refer to text, page 344, figure 12-20  Entamoeba (a protozoan) Organism that causes amoebic dysentery Its simpler life cycle summarized: – Amoebas multiply in large intestine – Some of the amoebas form a tough covering called a cyst; these are encysted amoebas – Amoebas are passed in feces; the cyst protects the amoeba when it’s in the environment – Human ingests contaminated food or water – Cyst helps amoeba resist stomach acid/digestion – Amoeba reaches the large intestine & multiplies  MCAP reproduction Can reproduce on own, but often require a living host to provide suitable environment Often have complex life cycles with several stages or forms (see pages 350 and 353) MCAPS (aka helminths) often require two or more hosts to complete their life cycle Egg laying occurs at some stage in life cycle  Culturing microbes in the lab Culturing microbes means growing microbes Microbes are cultured for many reasons – Research and education (to learn about them) – Identification (diagnosis) – To make vaccines (flu and polio vaccines) – Food production (dairy, beverages) – To produce drugs (antibiotics, insulin) – To produce chemicals (for industrial use)  Culturing bacteria and fungi Most are easily cultured in the lab Grown on culture media (artificial media) – Culture media provides nutrients – Usually made from animal or plant “extracts” – Most are either broths (liquid) or agars (solid) Organisms growing in culture media are called a “culture” Many bacteria (and fungi) are isolated from patient, cultured, and then identified Petri dish with bacterial (Kingdom Eubacteria) colonies Petri dish with mold (Kingdom Fungi) colonies Four different molds on a petri dish  Identifying protozoans and MCAPs The growth of protozoans and MCAPs is closely linked to the host; the host provides a complex set of conditions needed for growth It is hard to culture these organisms in the lab because it is difficult or impossible to duplicate the conditions they need for growth Identification is done by direct observation of the parasite or parasite eggs in a sample ID is key step in treating infectious disease Sporozoites of Plasmodium (malaria) from mosquito salivary glands. Magnification 1000X Cells of Trypanosoma (a protozoan) in human blood. Trypanosoma is dark blue. Round cells are red blood cells.  Culturing viruses Viruses require living cells to reproduce To culture viruses in the lab, some type of living cells must be provided, such as: – Live lab animals (mice, rats) – Embryonated eggs (injected through shell) – Cell cultures (living cells in liquid growth media) Cells & growth media (for cells) in test tubes or bottles After virus added, cells may become infected Infected cells look different than non-infected ones Cell culture media. The red liquid has living cells for virus multiplication. Cells from cell culture media. Image A – healthy. Image B – virus-infected.  Normal microbiota [Reading: pages 2-5 and 394-395] The normal microbiota (nmb) is often called the human microbiome, or just microbiome Normal microbiota is a term that refers to the microbes, mostly bacteria & some yeasts, that colonize different areas of the body Having nmb is perfectly natural & normal The relationship between humans and their microbiome is complex and important  Normal microbiota The nmb usually protects us from illness The nmb do not normally cause disease The nmb usually interferes with the growth of pathogenic microbes and protects us But members of the nmb can cause disease when growing outside their normal location Escherichia coli in the colon helps us but it can cause urinary tract infections & do harm  Normal microbiota (continued) Found on/in skin, eyes, mouth, nose, throat, intestines, and the urogenital tract The nmb is not found in the blood, brain, lungs, kidneys, or other internal organs If a member of the nmb locates to an area of the body where it is not usually found, it can cause an infection and disease can result Healthy nmb protects the body from infection and illness by microbial antagonism  Microbial antagonism [[Reading: page 397and 398] Ways in which normal microbiota (nmb) can prevent the growth of harmful microbes – They out-compete harmful microbes for habitat and nutrients (crowd out harmful microbes) – The nmb alters environmental conditions in their favor (like change pH or use up available O2) – Some members of the nmb produce toxins that kill other microbes; toxins called bacteriocins The nmb normally protects us from illness !  Opportunistic pathogens [Reading: page 398] Usually “harmless” microbes that can cause disease if given an “opportunity” (page 398) Opportunistic pathogens can’t “invade” the body on their own, but require “help” – Wounds, breathing aids, burns, urinary catheter – “Help” can be considered a predisposing factor Contrast them with true pathogens which can invade the host without predisposing factors  Opportunistic infections examples Staphylococcus aureus – Part of nmb of about 2 in 5 people (40%) – On skin & mucus membranes of nose and throat – Can infect wounds, cause pneumonia, infect the urinary tract, cause toxic shock, and much more Candida albicans – Found in mucus membranes of all people – This yeast can overpopulate mucus membranes due to use of strong antibiotics & other reasons – Thrush; female reproductive tract infections  Opportunistic infections examples (continued) Escherichia coli (E. coli) in intestines OK – In urethra, it may cause urinary tract infection – E. coli in a wound may cause infection – If introduced to lungs, it causes pneumonia Klebsiella pneumoniae, nmb of intestines – Causes pneumonia if in the lungs – Causes other diseases, but OK in intestines! The human nmb contains many of the most common opportunistic pathogens  Opportunists -- WebMD Links (press and hold control key to activate link) https://www.webmd.com/a-to-z-guides/klebsi ella-pneumoniae-infection#1 https://www.webmd.com/skin-problems-and- treatments/guide/what-is-candidiasis-yeast-i nfection#2  Koch’s postulates [Reading: pages 398 and 399] Set of rules for proving that a particular microbe causes a specific disease: – The suspected pathogen must be present in all cases of the disease being studied – The pathogen must be isolated from a sick host and a pure culture of it must be grown in the lab – The isolated pathogen must cause the same disease when inoculated to a lab animal – The suspect pathogen must be recovered from the inoculated lab animal  Epidemiology Definition—study of when and where diseases occur and how they spread – Etiology-cause of disease (HIV causes AIDS) – Transmission-spread of disease (many ways) – Incidence-how many cases; location of cases Goals of epidemiology – Main goal: break the chain of transmission – Keep records, promote awareness  Spread of infection [Reading: pages 403-407] Reservoir—source of pathogens – Human beings: principal reservoir – Animals: domestic and wild – Non-living: soil and water Transmission—movement of pathogens – Direct: person-to-person – Indirect: through fomite – Vehicle: through food, water, air – Vector: arthropod (mainly mosquitoes & ticks)  Disease transmission Person-to-person by direct contact – Microbe moves directly from one host to the next – Through close contact like touching, kissing, being coughed/sneezed upon Person-to-person by indirect contact – Germ from: infected host → fomite → new host – Fomite: any non-living object involved in spread of disease, like a used tissue; not food or water ~85% of illnesses transmitted in these ways  Disease transmission (continued) Vehicle transmission – Diseases transmitted in food, water, or air – Contaminated water: amoebic dysentery – Food poisoning: caused by Salmonella & others Vector transmission – Diseases transmitted, or spread, by arthropods; mosquitoes & ticks are the most common vectors – Vector: living thing that transmits microbes – Malaria (mosquito) and Lyme Disease (ticks)