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CHAPTER 1 – AN INVISIBLE WORLD NOTES BIOL 115
Introduction microorganisms can be found In boiling thermal hot springs to deep beneath the Antarctic ice also called small organisms most cannot be seen without a microscope most are harmless to humans play a role in ecosystems, forming the backbone of many food webs also used to make biofuels, medicines, foods What our ancestors knew? Fermented foods and beverages foods and beverages like beer, wine, bread, yogurt, cheese, and pickled vegetables requires microbial fermentation a process that uses bacteria, mold, or yeast to convert sugars (carbohydrates) to alcohol, gases, and organic acids. For example, yeast (a microorganism) – its cells metabolize the carbohydrates in flour, produce carbon dioxide and causes bread to rise. Early notions of disease, contagion and containment ancient civilizations had some understanding that disease could be transmitted by things they could not see. For example, quarantining people with leprosy ( a disease that progresses slowly)- people were likely quarantined after they spread the disease. Greek- malaria (miasmatic odors) attributed to bad air – developed hygiene practices Rome- brought a giant sewer and fresh water into the city The Greek physician Hippocrates (460–370 BC) is considered the “father of Western medicine” believed that diseases were not caused by supernatural forces instead from natural forces from within patients or their environments Hippocratic corpus – a collection of texts that make up some of the oldest surviving medical books Hippocratic Oath, taken by new physicians to pledge their dedication to diagnosing and treating patients without causing harm
Greek philosopher and historian Thucydides(460–395 BC) is considered the father of scientific history because he advocated for evidence- based analysis of cause- and-effect reasoning. He observed that survivors of the Athenian plague were subsequently immune to the infection (concept of immunity). Marcus Terentius Varro (116–27 BC) Roman writer proposed that disease could be caused by “certain minute creatures... which cannot be seen by the eye The birth of microbiology a Dutch cloth merchant named Antonie van Leeuwenhoek (1632–1723) was the first to develop a lens powerful enough to view microbes in 1675, he was able to observe single-celled organisms, which he described as “animalcules” or “wee little beasties,” swimming in a drop of rainwater Louis Pasteur (1822-1895), a French chemist, showed that individual microbial strains had unique properties and demonstrated that fermentation is caused by microorganisms. He invented pasteurization, a process used to kill microorganisms responsible for spoilage and developed vaccines for the treatment of diseases, including rabies, in animals and humans Robert Koch (1843-1895) a German physician, was the first to demonstrate the connection between a single, isolated microbe and a known human disease. For example, he discovered the bacteria that cause anthrax (Bacillus anthracis), cholera (Vibrio cholera), and tuberculosis (Mycobacterium tuberculosis) A systematic Approach The science of taxonomy Taxonomy is the classification, description, identification, and naming of living organisms. Classification is the practice of organizing organisms into different groups based on their shared characteristics.
Micro connections – same name, different strain e.g. E.coli (disease causing) causes food poisoning. different strain of ecoli found naturally in your gut help us digest food. Types of Microorganisms Most microbes are unicellular and small enough that they require artificial magnification object must measure about 100 micrometres (μm) to be visible without a microscope for example, animal cell measures roughly 10 μm across but is still microscopic. Bacterial cells are typically about 1 μm, and viruses can be 10 times smaller than bacteria 0.1 nm to 1um needs electron microscope, 100nm- 1mm needs light microscope Microorganisms differ from each other not only in size but also in structure, habitat, metabolism and many other characteristics Some microbes such as viruses are acellular (not composed of cells) Units of Length Commonly Used in Microbiology Metric Unit Meaning of Prefix Metric Equivalent meter (m) — 1 m = 100 m decimeter (dm) 1/10 1 dm = 0.1 m = 10− m centimeter (cm) 1/100 1 cm = 0.01 m = 10− m millimeter (mm) 1/1000 1 mm = 0.001 m = 10−3 m micrometer (μm) 1/1,000,000 1 μm = 0.000001 m = 10−6 m nanometer (nm). 1/1,000,000,000 1 nm = 0.000000001 m = 10−9 m
Microorganisms are found in three domains of life: Archaea, Bacteria, Eukarya Microbes within bacteria and Archaea are all prokaryotes (their cell lack a nucleus) Microbes in Eukarya are eukaryotes (their cell have a nucleus) Prokaryotic Microorganisms
1. Bacteria Most bacteria are harmless or helpful but some are pathogens (disease causing in humans and other animals) Bacteria are prokaryotic bcoz their DNA is not housed within a true nucleus instead they have cell walls that contain peptidoglycan Common shapes include spherical (coccus), rod shaped (bacillus), or curved (spirillum, vibro, spirochete) Some bacteria are photosynthetic such as oxygenic cyanobacteria and anoxygenic green sulfur and green nonsulfur bacteria - they use energy derived from sunlight and fix carbon dioxide for growth Some are nonphotosynthetic- obtain energy from organic or inorganic compounds in their environment 2. Archea Cell walls do not contain peptidoglycan Cells walls are composed of a similar substance called pseudopeptidoglycan Can be found in nearly every habitat on earth like bacteria; very hot, very cold, acidic or basic Archea live in the human body but none have shown to be human pathogens **Eukaryotic Microorganisms
- Protists – Algae and protozoa** Informal grouping of eukaryotes that are not plants, animals or fungi
Other multicellular Fungi are Molds, long filaments that form visible colonies Found in many different environments, from soil to rotting food to dank bathroom corners Play a critical role in the decomposition of dead plants and animals Some molds can cause allergies, others produce disease-causing metabolites called mycotoxins. Decompose dead plants and animals. Used in making pharmaceuticals – penicillin (abx) and cyclosporine (used to prevent organ rejection following a transplant) Unicellular fungi such as yeast are found in many different environments from the deep sea to the human navel Some have beneficial uses such as causing bread to rise and beverages to ferment It can also cause food to spoil Candida albicans (a unicellular fungus) cause diseases like vaginal yeast infection, oral thrush
3. Helminths (multicellular parasitic worms) Large enough to see without a microscope but involves disease- causing microscopic eggs and larvae. The disease is caused by microscopic eggs and larvae which can’t be seen by the naked eye. An example of Helminths is the guinea worm, or Dracunculus medinensis , which causes dizziness, vomiting, diarrhea, and painful ulcers on the legs and feet when the worm works its way out of the skin. Infection occurs after drinking water containing fleas infected by guinea worm larvae Another example is the beef tapeworm, Taenia saginata , which infects cattle and humans. T. saginata eggs are microscopic (around 50 μm), but adult worms like the one shown here can reach 4–10 m, taking up residence in the digestive system. 4. Viruses (acellular microorganisms) Not composed of cells Acellular
It consists of proteins and genetic material either DNA or RNA, but never both—that are inert outside of a host organism. by incorporating themselves into a host cell, viruses can co-opt the host’s cellular mechanisms to multiply and infect other hosts. (Need a host cell to replicate). Can infect all types of cells Responsible for numerous diseases from the common cold to deadly ebola Many viruses do not cause disease Microbiology as a field of study bacteriology i s the study of bacteria mycology is the study of fungi protozoology is the study of protozoa parasitology is the study of helminths and other parasites virology i s the study of viruses Immunology is the study of the immune system Microbiologists can also specialize in certain areas of microbiology, such as clinical microbiology, environmental microbiology, applied microbiology, or food microbiology.
Summary
1.1 What Our Ancestors Knew
- Microorganisms (or microbes) are living organisms that are generally too small to be seen without a microscope.
- Throughout history, humans have used microbes to make fermented foods such as beer, bread, cheese, and wine.
- Long before the invention of the microscope, some people theorized that infection and disease were spread by living things that were too small to be seen. They also correctly intuited certain principles regarding the spread of disease and immunity.
- Antonie van Leeuwenhoek, using a microscope, was the first to actually describe observations of bacteria, in 1675.
- Microscopic fungi include moulds and yeasts.
- Helminths are multicellular parasitic worms. They are included in the field of microbiology because their eggs and larvae are often microscopic.
- Viruses are acellular microorganisms that require a host to reproduce.
- The field of microbiology is extremely broad. Microbiologists typically specialize in one of many subfields, but all health professionals need a solid foundation in clinical microbiology.
