Introduction to microbial world – B.Sc. 1st sem Notes

The COVID-19 pandemic highlighted the significance of microbiology, as scientists from various fields collaborated to address crucial questions about the nature, impact, treatment, and prevention of the virus.

Introduction to Microbial World

The concept of microbiology began with the discovery of the microscope by Anton Van Leeuwenhoek.

Basic microscopy deals with a diverse group of studies that help in research related to the biochemistry, physiology, cell biology, ecology, evolution, and clinical aspects of microorganisms, including the host response to these agents.

This chapter aims to introduce the microbial world, its diversity, biology, and subdisciplines within microbiology, emphasizing the unique properties and approaches required to understand microorganisms.

Microbiology 

The field of microbiology studies microorganisms, which are organisms too small to be seen clearly with the naked eye and are incredibly diverse and abundant.

Microbiology is the branch of science that deals with microscopic organisms and their interaction with other microscopic and macroscopic organisms.

Microorganisms are tiny microscopic organisms that are too small to be seen with the naked eye and thus, can only be seen with a microscope. Microorganisms include microscopic organisms like bacteria, fungi, archaea, protozoa, and viruses.

Microorganisms can be classified into two types:

1. Cellular and 
2. Acellular

1. Cellular microorganisms include bacteria, archaea, fungi, and protists.
2. Acellular microorganisms include viruses, viroids, satellites, and prions.

Cellular microorganisms are further distinguished by their cellular structure, with prokaryotic cells and eukaryotic cells having a nucleus and membrane-bound organelles.

Classification of Microorganisms

The five-kingdom classification system, which divided organisms into Monera, Protista, Fungi, Animalia, and Plantae, is no longer accepted due to the immense diversity among prokaryotes.

Progress in electron microscopy, biochemical analysis, and molecular techniques has greatly contributed to the classification and understanding of microorganisms.

The microbes are used for their unique features which allow the production of antibiotics, amino acids, hormones, and other therapeutic compounds, and also the production of food and food-related products.

Microorganisms are also involved in the decomposition of components. However, certain genetic features and biochemical abilities of microorganisms make them dangerous for industry (food spoilage) as well as human health.

With the establishment of microbiology as a discipline, the application of microorganisms in different areas has also increased.

The use of microorganisms in food and pharmaceuticals has given rise to the branching of microbiology into further disciplines and studies.

Thus, over the years, the branch has been classified into further groups like agriculture microbiology, food microbiology, pharmaceutical microbiology, systemic microbiology, etc.

The studies in microbiology have also increased due to the use of microorganisms in different researches as these are easy to manipulate and reproduce when compared to other living organisms.

Studies in microbiology are essential for the discovery of new and advanced methods for the discovery of emerging microorganisms and associated diseases and applications.

Microbiology also deals with techniques for the identification of these microorganisms, their classification, and the life cycle.

All of this allows for a better understanding of microorganisms and their role in maintaining the ecosystem.

Microbiology and microorganisms can be applied for the formation of new genetically engineered microorganisms by a process like genetic recombination.

Besides, different microorganisms have found their application in the production of food, industrial products, and antibiotics.

Aim of Microbiology 

1. Understanding Microbial Diversity:

To gain knowledge about the diversity of microorganisms, including bacteria, viruses, fungi, and protozoa.

2. Microbial Classification and Taxonomy: 

To learn the principles of classifying and naming microorganisms.

3. Microbial Structure and Function:

To study the detailed structure and functions of microbial cells.

4. Genetics and Molecular Biology of Microorganisms: 

To understand the genetic makeup and molecular biology of microorganisms.

5. Ecological Roles of Microorganisms:

To explore the roles of microorganisms in various ecosystems.

6. Economic Importance of Microorganisms: 

To learn about the applications of microorganisms in different fields.

7. Microbial Techniques and Methodologies: 

To acquire practical skills in isolating, culturing, and identifying microorganisms.

8. Pathogenic Microorganisms and Human Health: 

To study the role of microorganisms in human health and disease.

9. Biotechnological Applications of Microorganisms: 

To understand the use of microorganisms in biotechnology.

10. Environmental Impact and Microbial Ecology: 

To investigate the impact of microorganisms on the environment.

Scope of Microbiology

There is vast scope in the field of microbiology due to the advancement in the field of science and technology.

The scope in this field is immense due to the involvement of microbiology in many fields like medicine, pharmacy, diary, industry, clinical research, water industry, agriculture, chemical technology and nanotechnology.

The study of microbiology contributes greatly to the understanding of life through enhancements and intervention of microorganisms. There is an increase in demand for microbiologists globally.

• Genetics: Mainly involves engineered microbes to make hormones, vaccine, antibiotics and many other useful products for human being. Development of new microbial strains that are more efficient in synthesizing useful products.

• Agriculture:
  • The influence of microbes on agriculture; the prevention of the diseases that mainly damage the useful crops.
  • Try to combat plant diseases that attack important food crops, work on methods to increase soil fertility and crop yields etc.
  • Currently there is a great interest in using bacterial or viral insect pathogens as substitute for chemical pesticides.

• Food science: It involves the prevention of spoilage of food and food borne diseases and the uses of microbes to produce cheese, yoghurt, pickles and beer. 

• Immunology: The study of immune system which protect the body from pathogens.

• Medicine: deals with the identification of plans and measures to cure diseases of human and animals which are infectious to them.

• Industry: it involves use of microbes to produce antibiotics, steroids, alcohol, vitamins and amino acids etc.

• Microbial ecology: biogeochemical cycles, bioremediation to reduce pollution effects

• Microbial physiology and Biochemistry: Study the synthesis of antibiotics and toxins, microbial energy production, microbial nitrogen fixation, effects of chemical and physical agents on microbial growth and survival etc.

• Microbial genetics and Molecular biology – nature of genetic information and how it regulated the development and function of cells and organisms. 

• Genetic engineering: Engineered microorganisms are used to make hormones, antibiotics, vaccines and other products. New genes can be inserted into plants and animals.

Microbiologists and their Contributions

Anton Van Leeuwenhoek [1632-1723]

• Anton Van Leeuwenhoek  was a Dutch Philosopher, born on 24 October 1632.
• He is regarded as Father of “Bacteriology‟ and “Protozoology‟, because of his contribution to the field of bacteria and protozoa.
• He invented a simple microscope having magnification power up to 300X. And used them to become the first person to see and describe bacterial.
• He observed bacteria from his teeth scrap under the microscope invented by him and he named them as “animalcules”.
• He was a draper and owned a small goods shop in Delft, Holland. As a hobby he used to grind glass and make lenses.
• He fixed his lenses placing them between 2 silver or brass plates riveted together.
• At the shop, magnifying glasses were used to count the threads and inspect the quality of cloth. 
• He was inspired and taught himself new methods for grinding and polishing tiny lenses of great curvature, which gave magnification up to 275x, the finest known at that time.
• He also discovered bacteria in rainwater ditch and protozoans like paramecium and amoeba. Also observed a variety of things mainly out of curiosity, hair fibers, plant structure, insects, crystals , a variety of fluids such as pond water, blood etc
• He presented all his observations with illustration before the scientific organization “Royal Society of London‟ in 1683.

Louis Pasteur (1822-1895) 

A Pioneer in Microbiology

Louis Pasteur, born on December 27, 1822, in the quaint village of Dole, France, a renowned scientist and the “Father of Microbiology.” 

Initially trained as a chemist, Pasteur’s passion for scientific inquiry led him to transition into medicinal research, where he made groundbreaking contributions that revolutionized the field.

Pasteur’s remarkable discoveries

1. Tartaric Acid Crystallography: He identified two distinct types of crystals in tartaric acid, demonstrating the importance of microscopic observation in scientific research.

2. Microbial Fermentation: Pasteur’s investigations revealed the role of microorganisms in fermentation processes, dispelling the prevailing notion of spontaneous generation.

3. Aerobic Microbes: He discovered the existence of aerobic microbes, expanding our understanding of microbial diversity and their impact on various environments.

4. SilkWorm Disease: Pasteur’s research on silkworm disease saved the French silk industry by identifying the causative agent and developing preventive measures.

5. Anthrax and Rabies Research: Pasteur’s work on anthrax and rabies led to the development of vaccines, marking a significant milestone in disease prevention and immunology.

6. Pasteurization: His invention of pasteurization, a process of partial microorganism elimination, revolutionized food preservation and public health.

In recognition of his groundbreaking contributions, the Pasteur Institute was established in Paris with public support, serving as a testament to his enduring legacy. Pasteur died in Paris on September 28, 1895. 

Robert Koch (1843-1910)

• Robert Koch, a German bacteriologist, made significant contributions to the field of microbiology. 
• Born on December 11, 1843, in Germany, he obtained his medical degree in 1866 and initially practiced medicine. 
• However, his passion for microscopic studies led him to devote his full attention to this field.

• Koch’s groundbreaking discoveries include identifying the bacteria responsible for anthrax, septicemia, tuberculosis, and cholera. His methodologies enabled other researchers to identify numerous other critical pathogens.

Koch’s notable contributions

• Establishing the germ theory of diseases through his work on the anthrax bacillus.
• Discovering the tuberculosis bacillus.
• Introducing the technique of preparing bacterial smears on glass slides and staining them with aniline dyes.
• Developing the plate method for isolating pure bacterial cultures.
• Koch’s legacy continues to shape the field of microbiology, and his contributions have significantly advanced our understanding of infectious diseases. 

He passed away on May 27, 1910, leaving behind a remarkable body of work that continues to inspire and inform scientific research.

Joseph Lister (1827-1912)

• Joseph Lister, a renowned figure in the medical field, was born in England on April 5, 1827. 
• His contributions to the field of surgery are significant and have had a lasting impact on medical practices.

Educational Background and Career:

• Lister obtained his medical degree in 1852 and subsequently held prestigious positions as a professor of surgery at the University of Glasgow and later at King’s College London.

Groundbreaking Achievements:

• Lister made groundbreaking discoveries in the field of microbiology, becoming the first individual to successfully isolate bacteria in pure culture, specifically Bacillus lactis, using liquid cultures.

Contributions to Surgical Practices:

• Lister’s most notable contributions lie in his efforts to prevent wound infections during surgical procedures through the implementation of antiseptic methods. 
• He advocated for the use of carbolic acid soaped dressings to cover wounds, particularly in cases of compound fractures that were prone to inflammation. 
• This approach revolutionized surgical practices and significantly improved wound healing outcomes.

Joseph Lister’s dedication to advancing surgical techniques and his pioneering work in antiseptic methods have left an indelible mark on the medical field. 

His contributions continue to be recognized and celebrated, solidifying his legacy as a visionary surgeon and a pioneer in infection control.

Dmitri Ivanovsky (1864 – 1920)

Birth : 28 October 1864

Death: 20 June 1920

Dmitri Ivanovsky, a Russian botanist, stands as a giant in the history of microbiology for his groundbreaking discovery of viruses in the late 1890s. 

While investigating a devastating disease plaguing tobacco crops – Tobacco Mosaic Disease – Ivanovsky stumbled upon a phenomenon that revolutionized our understanding of infectious agents.

Discovery of Viruses (1890s):

• While studying tobacco mosaic disease, Ivanovsky discovered an infectious agent that could pass through a porcelain Chamberland filter known to block bacteria.
• This finding challenged the prevailing belief that bacteria caused all infectious diseases.
• His work laid the groundwork for the field of virology, though viruses weren’t formally named until later.

Characteristics of the Infectious Agent:

• Ivanovsky observed an infectious agent that could pass through a bacterial filter.
• This suggested the infectious agent was extremely small, even smaller than known bacteria.
• Although he couldn’t directly observe the agent, his experiments provided crucial clues about its properties.

Impact on Microbiology:

• Ivanovsky’s discovery opened a new chapter in microbiology by demonstrating the existence of a new class of infectious agents, viruses.
• It led to further research on viruses and their role in various diseases.
• Ivanovsky also conducted research on yeast fermentation, photosynthesis.
• Ivanovsky also contributed to the field of agricultural microbiology.
• He is credited alongside Martinus Beijerinck, who independently discovered viruses around the same time.

Martinus W. Beijerinck

• Martinus W. Beijerinck, a Dutch microbiologist, was born on March 16, 1851, in Amsterdam, Netherlands. 
• He made significant contributions to the field of microbiology, particularly in the study of viruses and bacteria.
• Beijerinck is widely recognized for his groundbreaking discovery that viruses are distinct entities capable of reproduction, setting them apart from other organisms.
• His most notable achievement was the development of the enrichment culture technique in 1888, which revolutionized the field.
• Furthermore, Beijerinck’s exploration of soil led to the discovery of novel bacterial species. 
• He also provided a detailed account of biological nitrogen fixation, a crucial process that converts nitrogen gas into a form usable by plants. 
• His isolation of Bacillus radicicola and subsequent demonstration of its role in forming nodules on the roots of leguminous plants (later known as Rhizopus) further solidified his expertise.
• In 1904, Beijerinck made another breakthrough by uncovering the phenomenon of bacterial sulfate reduction, a form of anaerobic respiration. 
• His contributions to environmental microbiology and virology have earned him recognition as a pioneer in these fields.