Exploring the Microscopic World: the Distinguishing
Features of Bacteria, Fungi and Viruses
Introduction
In the microscopic world of pathogens, bacteria, fungi, and viruses are three big players, each
with unique characteristics. With the help of diagrams, this essay unveils the defining features
of the three, covering cell structure, the flow of genetic information, and replication.
The knowledge of the structure of different forms of microscopic pathogens has helped us to
understand their impact on life, which has had critical implications for the medical field.
Cell Structure
Bacteria are single cellular prokaryotes, meaning they lack a nucleus and other membrane-
bound organelles. Where eukaryotic genomes are often organized into multiple chromosomes
in the nucleus, bacteria contain one bacterial chromosome that is contained in the nucleoid
(listed as nuclear matter in Figure 1). Bacteria also have plasmids: smaller, circled
extrachromosomal DNA in their cytoplasm. Figure 1 shows the defining features of bacterial
cell structure. Shown in the figure is one flagellum, though bacteria can have multiple flagella.
Their typical function is to propel the cell body through liquid.
Figure 1: The cellular structure of a generalised bacterium
Besides a cell membrane, bacteria also have a cell wall, which is not present in eukaryotic
organisms. There are two types of bacterial cell walls: gram-positive and gram-negative, shown
in Figure 2.
Figure 2: two different types of bacterial cell walls; gram-positive and gram-negative
Features of Bacteria, Fungi and Viruses
Introduction
In the microscopic world of pathogens, bacteria, fungi, and viruses are three big players, each
with unique characteristics. With the help of diagrams, this essay unveils the defining features
of the three, covering cell structure, the flow of genetic information, and replication.
The knowledge of the structure of different forms of microscopic pathogens has helped us to
understand their impact on life, which has had critical implications for the medical field.
Cell Structure
Bacteria are single cellular prokaryotes, meaning they lack a nucleus and other membrane-
bound organelles. Where eukaryotic genomes are often organized into multiple chromosomes
in the nucleus, bacteria contain one bacterial chromosome that is contained in the nucleoid
(listed as nuclear matter in Figure 1). Bacteria also have plasmids: smaller, circled
extrachromosomal DNA in their cytoplasm. Figure 1 shows the defining features of bacterial
cell structure. Shown in the figure is one flagellum, though bacteria can have multiple flagella.
Their typical function is to propel the cell body through liquid.
Figure 1: The cellular structure of a generalised bacterium
Besides a cell membrane, bacteria also have a cell wall, which is not present in eukaryotic
organisms. There are two types of bacterial cell walls: gram-positive and gram-negative, shown
in Figure 2.
Figure 2: two different types of bacterial cell walls; gram-positive and gram-negative
