Microbiology: Definition and History

Introduction

The history of microbiology as a science owes an enormous debt to two inventors Robert Hooke and Antony van Leeuwenhoek, who extended the vision of biologists to the cellular level. Robert Hooke (1635-1703), an Englishman, designed scientific instruments of various kinds, in- cluding the compound microscope. The compound microscope had a lens at each end of the tubular body and an objective lens near the specimen, which produces an initial magnified image, and an ocular lens (eyepiece) near the observer’s eye, which magnifies the first image still further.

Although crude compound microscopes had existed since 1595, Hooke improved the optics and invented several helpful features found in the microscope today such as the stage to hold the specimen, an illuminator, and a course and fine focus controls. Hooke became particularly interested in microscopic examination of such materials as insects, plants, tissues and animal parts. In 1665 he observed what he called microscopic mushrooms which later was identified as the common bread mold.

Get quality help now

Bella Hamilton

Verified writer

Proficient in: Biology

5 (234)

“ Very organized ,I enjoyed and Loved every bit of our professional interaction ”

+84 relevant experts are online

Hire writer

Antony van Leeuwenhoek (1635-1723), a Dutch textile merchant, invented a simple (single-lens) microscope, originally for the purpose of examining the weave of fabrics. His microscope was a bead-like lens mounted in a metal plate equipped with a movable clip. He looked at a drop of lake water through a glass lens he had carefully made. Although many people before him had used curved glass to magnify objects. Leeuwenhoek's skilled hands made a lens that uncovered a startling and amazing sight, the world of microbes. Leeuwenhoek began submitting his observations to the Royal Society of London in 1673.

As he examined the drop of lake water he was astonished to find a variety of microorganisms he called, 'little animalcules'. Both men deserve credit for revealing the world of microbes, although there were many others who attributed to microbiology. Microbiology is the study of the microbes.

Microorganisms are too small to be seen with the naked eye, including bacteria, protozoa, and some fungi and algae. The microbial world also includes viruses and other infectious agents that are not considered organisms because they are not composed of cells; they are acellular. Microorganisms are the foundation for all life on earth. They have existed on this planet for 3.5 billion years, and over this time, plants, animals and modern microorganisms have evolved from them. They are the driving force in the evolution of all living things and our lives depend on their activities.

Identification of bacteria is extremely important because it plays an essential role in human health. Normal microbiota prevent disease by competing with disease-causing microbes. They help to degrade food that the body cannot digest and promote development of the immune system. An individual is less likely to develop allergies, asthma and other diseases due to early exposure to common microorganisms. An additional clinical relevance of microorganisms is the fact that they are masters of recycling, and without them we would run out of nutrients. They contribute to the atmospheric environment by replenishing the supply of oxygen which is needed to live. Nitrogen is also a vital part of nucleic acids and proteins. Nitrogen is crucial because certain microbes convert nitrogen into a form of nitrogen (the most common gas in the atmosphere) that other organisms can use called nitrogen-fixation. Life as we know it would not exist without nitrogen-fixing microbes.

Microorganisms are used in food production. Bacteria such as yeast are used to make bread and beer. Fermented milk products aid in producing foods for instance yogurt, cheese, and buttermilk. Probiotics also come from fermented milk which provide health benefits in protecting against digestive disruptions. Bacteria also degrade various environmental pollutants. Microorganisms synthesize a wide variety of different products for instance antibiotics used in treatment of diseases, amino acids used as dietary supplements; and polyhydroxybutyrate used in manufacturing of disposable diapers and plastics.

Information learned by studying microorganisms leads to easier production of many medications such as insulin. Bacteria can be used to obtain results very quickly because they grow rapidly and form billions of cells per millimeter on simple inexpensive growth media. Therefore they are study tools that have the same fundamental metabolic and genetic properties as higher life forms, because they synthesize their cell structures by similar mechanisms. This is necessary to manufacture antibiotics and vaccinations to treat, reduce, destroy and prevent infectious diseases also known as pathogens.

Gram staining is important because it is used to differentiate bacteria into two fundamental varieties of cells. Gram positive bacteria and Gram negative bacteria. The staining response is based on the chemical structure make up of the cell walls of both varieties of bacteria. Gram positives have a thick, relatively impermeable wall that resists decolorization and is composed of peptidoglycan and secondary polymers. Gram negatives have a peptidoglycan layer plus an overlapping lipid-protein bilayer which can be disrupted by decolorization. There are four major steps in Differential Gram staining. Crystal Violet the first step and primary stain. Mordant's Iodine, the second step. Decolorizing Alcohol, the third step. Safranin a counterstain, the fourth step.

The complete procedure and steps of Gram staining is described in the materials and methods section. A pure culture is a population descended from a single cell and contains only one species. A solid culture medium is in a container to hold and maintain the medium in an aseptic condition and a method to separate individual microbial cells. All containers, media and instruments must be sterile. Microbial cells supplied with the right nutrients and environment will multiply and form a colony. These colonies grow and are used in procedures like the MacConkey agar media, it is used to properly identify bacteria. Each species of bacteria has a unique biochemical footprint.

An API 20E (Analytical Profile Index) is a standardized identification system for Enterobacteriaceae. These tests are inoculated with a bacterial suspension that reconstitutes the media in 20 microtubules in a strip containing dehydrated substrates. The 20 microtubules are separated into groups. Several reagents are added to the API strip, there is also an incubation period (24 hours). The 20 microtubules undergo metabolism which produces color changes during incubation. The numerical profile consists of adding the values that correspond to positive reactions in each group. A 7- digit profile number is obtained and inserted into the API manual. Identification of the unknown bacteria now is identified.