1: Introduction to Microbiology (2023)

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    Obviously microbes are small. The traditional definition describes microbes as organisms or agents that are invisible to the naked eye, indicating that one needs assistance in order to see them. That assistance is typically in the form of a microscope of some type. The only problem with that definition is that there are microbes that you can see without a microscope. Not well, but you can see them. It would be easy to dismiss these organisms as non-microbes, but in all other respects they look/act/perform like other well-studied microbes (who follow the size restriction).

    So, the traditional definition is modified to describe microbes as fairly simple agents/organisms that are not highly differentiated, meaning even the multicellular microbes are composed of cells that can act independently– there is no set division of labor. If you take a giant fungus and chop half the cells off, the remaining cells will continue to function unimpeded. Versus if you chopped half my cells off, well, that would be a problem. Multicellular microbes, even if composed of billions of cells, are relatively simple in design, usually composed of branching filaments.

    It is also acknowledged that research in the field of microbiology will require certain common techniques, largely related to the size of the quarry. Because microbes are so small and there are so many around, it is important to be able to isolate the one type that you are interested in. This involves methods of sterilization, to prevent unwanted contamination, and observation, to confirm that you have fully isolated the microbe that you want to study.

    Microbe Size

    Since size is a bit of theme in microbiology, let us talk about actual measurements. How small is small? The cellular microbes are typically measured in micrometers (µm). A typical bacterial cell (let us say E. coli) is about 1 µm wide by 4 µm long. A typical protozoal cell (let us say Paramecium) is about 25 µm wide by 100 µm long. There are 1000 µm in every millimeter, so that shows why it is difficult to see most microbes without assistance. (An exception would be a multicellular microbe, such as a fungus. If you get enough cells together in one place, you can definitely see them without a microscope!)

    When we talk about the acellular microbes we have to use an entirely different scale. A typical virus (let us say influenza virus) has a diameter of about 100 nanometers (nm). There are 1000 nanometers in every micrometer, so that shows why you need a more powerful microscope to see a virus. If a typical bacterium (let us pick on E.coli again) were inflated to be the size of the Statue of Liberty, a typical virus (again, influenza virus works) would be the size of an adult human, if we keep the correct proportions.


    The Discovery of Microbes

    The small size of microbes definitely hindered their discovery. It is hard to get people to believe that their skin is covered with billions of small creatures, if you cannot show it to them. “Seeing is believing,” that is what I always say. Or someone says that.

    In microbiology, there are two people that are given the credit for the discovery of microbes. Or at least providing the proof of their discovery, both around the same time period:

    Robert Hooke (1635-1703)

    Robert Hooke was a scientist who used a compound microscope, or microscope with two lenses in tandem, to observe many different objects. He made detailed drawings of his observations, publishing them in the scientific literature of the day, and is credited with publishing the first drawings of microorganisms. In 1665 he published a book by the name of Micrographia, with drawing of microbes such as fungi, as well as other organisms and cell structures. His microscopes were restricted in their resolution, or clarity, which appeared to limit what microbes he was able to observe.

    Antony van Leeuwenhoek (1632-1723)

    Antony van Leeuwenhoek was a Dutch cloth merchant, who also happened to dabble in microscopes. He constructed a simple microscope (which has a single lens), where the lens was held between two silver plates. Apparently he relished viewing microbes from many different sample types – pond water, fecal material, teeth scrapings, etc. He made detailed drawings and notes about his observations and discoveries, sending them off to the Royal Society of London, the scientific organization of that time. This invaluable record clearly indicates that he saw both bacteria and a wide variety of protists. Some microbiologists refer to van Leeuwenhoek as the “Father of Microbiology,” because of his contributions to the field.

    Microbial Groups

    Classification of organisms, or the determination of how to group them, continually changes as we acquire new information and new tools of assessing the characteristics of an organism. Currently all organisms are grouped into one of three categories or domains: Bacteria, Archaea, and Eukarya. The Three Domain Classification, first proposed by Carl Woese in the 1970s, is based on ribosomal RNA (rRNA) sequences and widely accepted by scientists today as the most accurate current portrayal of organism relatedness.

    1: Introduction to Microbiology (2)

    Tree of Life.


    The Bacteria domain contains some of the best known microbial examples (E. coli, anyone?). Most of the members are unicellular, cells lack a nucleus or any other organelle, most members have a cell wall with a particular substance known as peptidoglycan (not found anywhere else but in bacteria!), and humans are intimately familiar with many members, since they are common in soil, water, our foods, and our own bodies.


    Archaea is a relatively new domain, since these organisms used to be grouped with the bacteria. There are some obvious similarities, since they are mostly unicellular and cells lack a nucleus or any other organelle. But they have completely different cell walls that vary markedly in composition (but notably lack peptidoglycan) and their rRNA sequences have shown that they are not closely related to the Bacteria at all. In fact, they appear to be more closely related to the eukaryotes! These organisms are found in soil, water, even sometimes in the human body, but they are also found in some very extreme environments on Earth – very cold, very hot, very salty, very pressurized, very acidic, earning them the commonly used name “the extremophiles,” or extreme-loving organisms.


    The Eukarya Domain includes many non-microbes, such as animals and plants, but there are numerous microbial examples as well, such as fungi, protists, slime molds, and water molds. The eukaryotic cell type has a nucleus, as well as many organelles, such as mitochondria or endoplasmic reticulum.


    Viruses are not part of the Three Domain Classification, since they lack ribosomes and therefore lack rRNA sequences for comparison. They are classified separately, using characteristics specific to viruses. Viruses are typically described as “obligate intracellular parasites,” a reference to their strict requirement for a host cell in order to replicate or increase in number. These acellular entities are often agents of disease, a result of their cell invasion.

    Taxonomic Ranks

    Taxonomic ranks are a way for scientists to organize information about organisms, by determining relatedness. Domains are the largest grouping used, followed by numerous smaller groupings, where each smaller grouping consists of organisms that share specific features in common. Each level becomes more and more restrictive as to whom can be a member. Eventually we get down to genus and species, the groupings used for formation of a scientific name. This is the binomial nomenclature devised by Carl Linnaeus in the 1750s.

    1: Introduction to Microbiology (3)

    Taxonomic Ranks. By Annina Breen (Own work) [CC BY-SA 4.0], via Wikimedia Commons

    Binomial Nomenclature

    When referring to the actual scientific name assigned to an organism, it is important to follow convention, so it is clear to everyone that you are referring to the scientific name. There are rules in science (just like in English class, where you would never refer to “mr. robert louis stevenson,” or at least not without expecting to get your paper back with red all over it).

    A scientific name is composed of a genus and a species, where the genus is a generic name and the species is specific. The species name, once assigned, is permanent for the organism, while the genus can change if new information becomes available. For example, the bacterium previously known as Streptococcus faecalis is now Enterococcus faecalis because sequencing information indicates that it is more closely related to the members of the Enterococcus genus. It is important to note that it is inappropriate to refer to an organism by the species alone (i.e. you should never refer to E. coli as “coli” alone. Other bacteria can have the species “coli” as well.)

    Now for the rules: The genus is always capitalized. The species is always lowercase. And both the genus and the species are italicized (common if typewritten) or underlined (common if handwritten). The genus may be shortened to its starting letter, but only if the name has been referred to in the text in its entirety at least once first (the exception to this is E. coli, due to its commonality, where hardly anyone spells out the Escherichia genus anymore).

    Key Words

    microbiology, microorganisms, microbes, unicellular, multicellular, differentiation, sterilization, observation, micrometers (µm), nanometers (nm), Robert Hooke, compound microscope, Antony van Leeuwenhoek, simple microscope, Royal Society of London, Father of Microbiology, Three Domain Classification, ribosomal RNA (rRNA), Bacteria, Archaea, Eukarya, obligate intracellular parasites, taxonomic ranks, genus, species, binomial nomenclature

    Study Questions

    1. Who are the members of the microbial world?
    2. What is the complete definition of microbiology? What characteristics are relevant?
    3. What size are different groups of microbes?
    4. What were the contributions of Hooke and Van Leeuwenhoek to the field of microbiology? How did they make these contributions?
    5. What is the basis for Woese’s classification and what are the three domains?
    6. What are the basic characteristics of members of the three domains? Where do microbes fit in?
    7. What are the basic characteristics of viruses? Why are they not classified in one of the three domains?
    8. What are taxonomic ranks? What is the system of binomial nomenclature? What are the basic rules? How are bacteria named? What is a genus and species? Be able to write a bacterial name correctly.


    1: Introduction to Microbiology? ›

    Introduction to Microbiology

    Microbiology is the study of a variety of living organisms which are invisible to the naked eye like bacteria and fungi and many other microscopic organisms. Although tiny in size these organisms form the basis for all life on earth.

    What is the introduction to microbiology? ›

    Introduction to Microbiology

    Microbiology is the study of a variety of living organisms which are invisible to the naked eye like bacteria and fungi and many other microscopic organisms. Although tiny in size these organisms form the basis for all life on earth.

    What do you learn in microbiology 1? ›

    The Microbiology major deals with microscopic organisms, such as bacteria, fungi, algae, protozoa, & viruses. Microbiology students study microbial growth, survival, metabolism, genetics, and physiology, while examining the organism's relationship to the environment, biotechnology, and diseases.

    Is intro to microbiology hard? ›

    Microbiology is hard. Some theories, such as that you should possess this or that knowledge before studying microbiology, make the situation harder. Maybe some background in biology or chemistry won't hurt, but you are going to college after all, where you'll get all the learning you need from scratch.

    What does intro to microbiology cover? ›

    Topics covered include: microbial taxonomy, morphology, staining, culture techniques, metabolism and physical and chemical methods for microbial control. General concepts in immunology, including host defense mechanisms, hypersensitivity and specific microbial diseases are also covered.

    What is basic microbiology for beginners? ›

    Microbiology is the study of microscopic organisms (microbes), which are defined as any living organism that is either a single cell (unicellular), a cell cluster, or has no cells at all (acellular). This includes eukaryotes, such as fungi and protists, and prokaryotes.

    What is the main study of microbiology? ›

    Microbiology is the study of the biology of microscopic organisms - viruses, bacteria, algae, fungi, slime molds, and protozoa. The methods used to study and manipulate these minute and mostly unicellular organisms differ from those used in most other biological investigations.

    How do you pass microbiology? ›

    Get a few more tips to help you plan your study time.
    1. Complete Prerequisites. ...
    2. Read Your Textbook. ...
    3. Take Notes in Class. ...
    4. Quiz Yourself. ...
    5. Participate in Class. ...
    6. Review Class Information. ...
    7. Join a Study Group.

    Why do I study microbiology? ›

    Though it sounds niche, microbiology is actually one of the most important sub-sectors of biology. By analysing microorganisms up close, microbiologists play a crucial role in combating disease, creating chemical products for agriculture, and even helping to keep the planet healthy.

    Why is it important to study microbiology? ›

    Microbiology has consistently proved to be one of the most significant fields in biology, making it possible to define how some microorganisms cause diseases, discover treatments for such diseases and even use a few microbes for industrial applications etc.

    What are the topics for microbiology class? ›

    Topics include the various groups of microorganisms, their structure, physiology, genetics, microbial pathogenicity, infectious diseases, immunology, and selected practical applications.

    What is the course content of microbiology? ›

    Course description

    Our BSc Microbiology course involves the study of microorganisms with particular emphasis on the biology of bacteria, viruses, fungi and protozoan parasites.

    What is the breakdown of microbiology? ›

    Microbiology is made up of several sub-disciplines, including: bacteriology (the study of bacteria), mycology (the study of fungi), phycology (the study of algae), parasitology (the study of parasites), and virology (the study of viruses, and how they function inside cells) [1].

    Is microbiology math heavy? ›

    Microbiologists regularly use complex mathematical equations and formulas in their work. Therefore, they need a broad understanding of math, including calculus and statistics.

    Is microbiology harder than chemistry? ›

    Is Microbiology Harder Than Chemistry? Comparing the two head-to-head, microbiology is the easiest but very objective-based. Chemistry is applied knowledge and is also dependent on simple algebra, formulas, and some calculations. All things that make it math-heavy than microbiology.

    Do you use microbiology in nursing? ›

    Microbiology helps a nursing professional to understand the basic concepts of reproduction, morphology, biochemical characteristics and genetics. Microbiology makes aware about new diseases and modern molecular identification methods.

    How do I prepare for a microbiology interview? ›

    Here are some additional tips to help you prepare for your microbiology job interview:
    1. Conduct research about the company. ...
    2. Practice answering interview questions with a friend. ...
    3. Make a list of examples. ...
    4. Plan your outfit ahead of time. ...
    5. Print copies of your resume and cover letter. ...
    6. Arrive early for your interview.
    Feb 16, 2023

    What are the two branches of microbiology? ›

    Microbiology can be divided into two branches: pure and applied. The former is the most fundamental branch, in which organisms themselves are examined in-depth. In applied microbiology, the organisms themselves are not studied but are applied to a certain process.

    How is microbiology used in everyday life? ›

    Microbiology applied in everyday life; in food production, biodegradation, commercial-product production, biotechnology and genetic engineering. There are various dishes in which microorganisms are needed. For example, for the making of curd and cheese, microorganisms are needed.

    Why is microbiology important in healthcare? ›

    Microbiologists and virologists diagnose, treat and prevent the spread of infection, making a major contribution to clinical infection management. Both roles demand excellent clinical skills as well as first-class laboratory knowledge.

    What is the difference between biology and microbiology? ›

    Biology deals with both macroscopic and microscopic organisms. Microbiology deals only with microscopic organisms. This concludes the major difference between Biology and Microbiology.

    Why do nurses need to know microbiology? ›

    Background. Nurses are responsible for implementing appropriate measures to reduce hospital infections, especially with multidrug resistant bacteria, so nursing students should learn about microbiology. This helps them to understand bacterial dissemination and infectious disease control.

    How many hours should you study for microbiology? ›

    The amount of study time recommended for a college level class such as microbiology, is a minimum of 2 hours for every hour your class meets.

    Should you take chemistry before microbiology? ›

    Many schools across the country offer microbiology without requiring any prerequisite biology or chemistry course. Students could be brand new traditional college students or non-traditional students who haven't had a science course in decades, and they can sign up for microbiology in their first semester!

    Why is microbiology so hard to study? ›

    Microbiology is a hard subject to study. It's very detail heavy; requiring you to remember a lot of facts about microscopic organisms, morphologies and modes of action. Without some basic knowledge of biology and chemistry, or the ability to memorize things easily, it's likely you'll struggle.

    What is interesting about microbiology? ›

    Microbiology's Influence is Huge

    In fact, life on Earth would not survive without microorganisms. Microbiology is an interdisciplinary science, overlapping aspects of several other academic branches such as chemistry, botany, zoology, physiology, genetics, medicine, nutrition and environmental science.

    Why is microbiology important to food safety? ›

    Microbiology is important to food safety, production, processing, preservation, and storage. Microbes such as bacteria, molds, and yeasts are employed for the foods production and food ingredients such as production of wine, beer, bakery, and dairy products.

    Are microbes made of cells? ›

    Microbes are single-celled organisms. Animal is a name reserved for multicellular eukaryotes that are heterotrophic, so organisms that are bigger than a single cell and almost all their cells have a nucleus.

    Does microbiology have math? ›

    Does microbiology need maths or physics? No. Microbiology neither requires Physics nor Mathematics.

    What are the three fields of microbiology? ›

    Fields of Microbiology

    Mycology: The study of fungi. Bacteriology: The study of bacteria. Virology: The study of viruses. Protozoology: The study of protozoa.

    What are the five scope of microbiology? ›

    The scope of microbiology is vast and extends to many areas of science. Over the years, the development of microbiology has been seen in the fields of medicine, pharmacy, clinical research, dairy industry agriculture, water industry, and Chemical Technology.

    What are the six major categories of microbiology? ›

    They can be divided into six major types: bacteria, archaea, fungi, protozoa, algae, and viruses.

    What are the six is of microbiology? ›

    These techniques are called the six “I's”: inoculation, incubation, isolation, inspection, information gathering, and identification.

    Is microbiology stressful? ›

    High. Stress is not uncommon amongst microbiologists, with daily work sometimes being quite demanding.

    What are the topics under Introduction to microbiology? ›

    Six Key Topics in Microbiology
    • Antimicrobial Resistance.
    • Environmental Microbiology.
    • Pathogenicity and Virulence.
    • Biotechnology and Synthetic Biology.
    • Microbiomes.
    • Food Microbiology.

    Why is introduction to microbiology important? ›

    Introduction. Although it may seem niche, microbiology is one of the most significant branches of biology. Microbiologists play an important role in disease prevention, the development of agrochemicals, and even the preservation of the environment by closely analysing microorganisms.

    What is microbiology course all about? ›

    Microbiology is the study of bacteria, yeasts and viruses at the level of protein and gene (molecular biology), at the level of the cell (cell biology and physiology), and at the level of the microbial community.

    Why is microbiology important to dental assistants? ›

    The dental assistant needs a foundation in microbiology to understand the nature of pathogens (disease-producing microorganisms) and how to prevent the transmission of disease in the dental office. The two major oral diseases, dental caries (decay) and periodontitis, are bacterial infections.

    How do I prepare for microbiology? ›

    Get a few more tips to help you plan your study time.
    1. Complete Prerequisites. ...
    2. Read Your Textbook. ...
    3. Take Notes in Class. ...
    4. Quiz Yourself. ...
    5. Participate in Class. ...
    6. Review Class Information. ...
    7. Join a Study Group.

    Why is microbiology important? ›

    Though it sounds niche, microbiology is actually one of the most important sub-sectors of biology. By analysing microorganisms up close, microbiologists play a crucial role in combating disease, creating chemical products for agriculture, and even helping to keep the planet healthy.

    Why is microbiology important for nursing? ›

    Microbiology helps a nursing professional to understand the basic concepts of reproduction, morphology, biochemical characteristics and genetics. Microbiology makes aware about new diseases and modern molecular identification methods.

    What is the role of microbiology in healthcare? ›

    Microbiology is a medical science where microbiologists are concerned with diagnosing infectious diseases and bringing out medical aid for that. The treatments and prevention are also part of microbiology. They study the various clinical supplication of microbes to better healthcare.

    What are the basic things a microbiologist should know? ›

    Microbiology techniques are required to study microorganisms' structure, function, metabolism, and genomics. They help understand how microbes work, interact with living organisms, cause diseases, and how they can be applied for human use.

    How important is microbiology for medical school? ›

    In addition, microbiology-related content is a significant component of medical education, and there are growing pressures to add more microbiology content to the medical curriculum as the scientific body of microbiology knowledge grows and as the emergence and prevalence of infectious diseases grows worldwide, ...

    Why is microbiology important in surgery? ›

    We cover microbiology as applied to surgical practice via basic science and principles of infection, including useful information about surgically important micro-organisms and antibiotics; and preventing infection in surgical patients.

    What are the three most common shapes of bacteria? ›

    The three basic shapes of bacteria are bacillus (rod-shaped), coccus (spherical-shaped), and spirillum (spiral-shaped). This simple model allows students to build the three shapes of bacteria in a short period of time.


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