Medical Microbiology

Anil K. Sharma, Girish Kumar Gupta, Mukesh Yadav, Anil K. Sharma, Girish Kumar Gupta, Mukesh Yadav

• Publisher: De Gruyter
• Year: 2022
• ISBN:
  9783110517743
• Edition: 1
• Topic: Physical Sciences
• Subtopic: Chemistry
• Index: Chemistry

Medical Microbiology is an excellent and easy-to-use textbook which explains the roles of microorganisms in human health and illness. Written in a clear and engaging manner, the book provides an overview of pathogenic organisms, their diagnosis and treatment tools as well as the molecular mechanisms of hostpathogen interactions and antimicrobial drug resistance.

Chapter 1 Introduction of microbiology

Pooja Mittal

School of Pharmaceutical Sciences, RIMT University, Mandi Gobindgarh

Ramit Kapoor

Parexal International, Mohali

Rupesh K. Gautam

Maharishi Markandeshwar University, Sadopur, Ambala

Abstract

Microbiology is a very broad area covering all aspects related to microorganisms including bacteria, archaea, fungi, protozoa, algae, virus and multicellular animal parasites. Microbiology represents a diverse and complex array of research in medical sciences, food technology and pharmaceutical industry, and has a great impact on world’s economy. This chapter deals with the basic aspects of microbiology, including microbial classification, cellular structure of bacteria and morphological forms of bacteria. The chapter also covers the basic aspects of microbial culture for the beginners.

Keywords: microbes, prokaryotes, eukaryotes, classification, culturing, diagnosis,

1.1 Introduction

Bacteria were initially observed by Anton von Leeuwenhoek in the late seventeenth century but his research was not recognized until the initial stages of nineteenth century. In the golden age of microbiology, Robert Koch, Louis Pasteur and their associates contributed a lot to the cause of microbiology [1, 2, 3]. Their methods of culturing microbes involved the cultivation of the bacteria from the natural environment and growing them in the artificial environment according to the need.

The word microbes or germs have been generally classified into three categories, i.e., animal, mineral or vegetable. Microbes, also called microorganisms, are the minute structures which are not visible to the naked eye, such as bacteria, fungi, protozoa, algae and virus.

Usually, we associate the microbes only with infections, diseases, spoilage of food and their other destroying effects; however, they also have many important contributions in maintenance of balance in nature. Marine and other freshwater microbes are essential in maintenance of aquatic food chain while soil microbes are responsible for the decomposition of the waste products and maintenance of the nitrogen cycle between soil and environment. Many commercial applications are also attributed to microbes as they can be used for the production of wine, alcohols, organic products and acids. Neutraceuticals and other food industries also use microbes for the production of vinegar, pickles, ketchup, soy sauce, green olives, buttermilk, cheese, yoghurt and bread [3].

1.2 Microbial classification

To understand about the pathogenicity of the microbes, we must have the knowledge about classification of the microbes. First, we will have a look at the major groups of microbes and their pattern of classification.

The major groups are:

1. Bacteria
2. Archaea
3. Fungi
4. Protozoa
5. Algae
6. Virus
7. Multicellular animal parasites

1.2.1 Bacteria

Bacteria (singular: bacterium) are simple unicellular microorganisms which contained prokaryotic (Greek meaning: prenucleus) cells as their genetic material is not enclosed by any membrane [2].

Bacterial cells may appear in various shapes like bacillus (rod like), coccus (spherical) and spiral (curved) mostly, while star-shaped and square-shaped bacteria were also seen some times. They may form some groupings, chains or clusters which are the characteristics of that particular genus or species. Bacterial cell wall generally consists of peptidoglycan (a carbohydrate and protein complex). They reproduce through the process known as binary fission which divides the bacterial cell into two equal parts. They feed themselves on the organic acids which are offered by the living or dead organisms of the nature. Bacteria can swim by using their appendages called flagella.

1.2.2 Archaea

Just like bacteria, they are also prokaryotes but their cell wall, if present, does not contain peptidoglycan. They exist in extreme environments. Based on their existence, they are categorized into three classes, viz. methanogens which release methane as their waste product, the extreme halophiles which live in the extreme salt environments like the Green Salt Lake and the Dead Sea and the extreme thermophiles thrive in the hot sulfurous water [3].

1.2.3 Fungi

These eukaryotes possess distinct nuclear matter which is covered by nuclear envelop or nuclear membrane. They can be unicellular or multicellular. Mushrooms are the typical example of multicellular fungi which have appearance like plants but photosynthesis process is not present in them. Chitin is present inside the cell wall of true fungi. The unicellular yeast has been known to be a primitive eukaryote which is bigger in size than bacteria.

1.2.4 Protozoa (singular – protozoan)

They are unicellular eukaryotes that move with the help of pseudopods (false feet), cilia or flagella. They contain variety of shapes and can live as free entities or as dependent on host (parasites). They can have both sexual and asexual modes of reproduction [4].

1.2.5 Algae

They are the eukaryotes that have photosynthetic ability. They can reproduce by sexual as well as asexual reproduction. The cell wall of algae is mostly composed of a complex carbohydrate called cellulose.

1.2.6 Virus

They are the different species which are acellular in nature. They contain single type of genetic material, either DNA (deoxyribonucleic acid) or RNA (ribonucleic acid) in the core, which is covered by a protein coat. They are dependent on other microbes for their reproduction. Thus, infection to the host cell is the proof of their livingness [5].

1.2.7 Multicellular animal parasites

They are not strictly the microorganisms but they are of intense medical importance. They thrive on the host animals. Majorly, two types of parasites exist, i.e., round worms and flat worms also called as helminthes [2, 4, 5, 6].

1.3 Bacterial morphology and cytology

Basically, the cells are divided into two basic types, i.e., prokaryotic cells and eukaryotic cells. Eukaryotic cells are more complex than prokaryotes. Plants and animal cells are of eukaryotic types, while bacterial cells are prokaryotic in nature. Bacteria and archaea are categorized into prokaryotes, while fungi, protozoans and algae are eukaryotes by nature. On the other hand, viruses are noncellular structures that do not fit their self in any of the above classifications [7, 8].

The bacterial cell generally ranges from 0.2 to 2 µm in ...

Table of contents

• Title Page
• Copyright
• Contents
• About the editors
• List of contributing authors
• Chapter 1 Introduction of microbiology
• Chapter 2 Bacteriology
• Chapter 3 Virology
• Chapter 4 Parasitology
• Chapter 5 Mycology
• Chapter 6 Microbial assay techniques
• Chapter 7 Antimicrobial resistance: medical science facing a daunting challenge
• Chapter 8 Microbiology as an occupational hazard: risk and challenges
• Chapter 9 Medical waste management
• Index