Members of the Bacterial World: Study with Video Lessons, Practice Problems & Examples

The microbial world consists of diverse organisms, categorized into living cellular organisms and nonliving acellular infectious agents. Cellular organisms are further divided into prokaryotes, like bacteria and archaea, which lack a nucleus, and eukaryotes, such as fungi and protists, which possess a nucleus. Acellular agents include viruses, viroids, and prions. Understanding these classifications is crucial, as bacteria and archaea, while both prokaryotic, are fundamentally different. This knowledge lays the foundation for exploring microbial diversity and its implications in various fields, including microbiology and medicine.

Members of the Bacterial World

In this video, we're going to begin our lesson on the members of the microbial world. And so there's actually a massive variety of microbes that exist within the microbial world. All of this variety is due to the fact that these microbes have been around for 1,000,000,000 of years, which is a really, really long time allowing them to develop and evolve in many different ways, leading to this massive variety. Now these microbes, as we discussed in some of our previous lesson videos, they can either be living organisms that are made of cells or they can be nonliving acellular infectious agents such as viruses, for example. And so by the term acellular, really what we mean is that they are not made of cells. And so microbes can either be living and made of cells or they can be nonliving and acellular, not made of cells. And we'll be able to see that down below in our image when we get there. Now these living organisms that are made of cells, they can either be prokaryotic, such as bacteria and archaea, or they can be eukaryotic, such as fungi, for example. And so if we take a look at our image down below at this map of the microbial world, what you'll notice is that this is an image that you can actually use as a map of our lesson on the microbial world. And so you can see at the very top, we have the microbial world, and it branches into two major groups. It branches into cellular organisms that are actually living and made of cells, and it also branches into acellular infectious agents that are acellular and not made of cells. And so as we move forward in our lesson, we are going to explore this map by following the leftmost branches first, and we'll continue to do that and zoom out as we go through our lesson. And so we'll cover the cellular organisms first, and then once we finish covering the cellular organisms, we'll zoom back out and talk about the acellular infectious agents. And so you can see, you can use this image as a reference and as a map of our lesson moving forward. And so what you can see here is that these cellular organisms, they can be branched into either prokaryotic organisms or prokaryotes or eukaryotic organisms or eukaryotes. Now notice that microbiologists will specifically focus on eukaryotes that are microscopic, microscopic eukaryotes. Now within this table, you can see that prokaryotes tend to be unicellular organisms made up of only one single cell. And prokaryotes do not have a nucleus, they have no nucleus. Whereas these eukaryotes that are over here, they can either be unicellular, again made of only one single cell, or they can be multicellular made up of many cells. And the eukaryotes, they do have a nucleus within the the cells. Now, looking at the prokaryotes over here, they branch into either bacteria or archaea. And moving forward, we'll be able to talk more about each of these different groups. Now notice that the eukarya over here, they can actually branch into many different groups, and not all of the groups are being shown here for the eukarya. However, what we are showing are the groups that microbiologists tend to focus on the most such as fungi, protists like algae and protozoa, and helminths. And so again, we'll be able to talk about each of these groups as we move forward in our course. Now for the acellular, infectious agents, they are grouped into three different categories, viruses, viroids, and prions. And once again, we'll be able to talk about each of these groups in more detail as we move forward in our course. However, this is a map of the microbial world that you should be familiar with and be able to group different, different groups under the appropriate label. So you should know that fungi, protists, and helminths are all part of the eukarya eukarya group and that viruses, viroids, and prions are part of the acellular infectious agents, and that the prokaryotes, would consist of bacteria and archaea. And so knowing those groupings will be important for you as you move forward in this course. Now, one thing to note is that the bacteria and archaea, which are over here listed under the prokaryotes, many students tend to think that bacteria and archaea are pretty much identical. However, it's important to note that bacteria and archaea are actually as different from each other as they are from the eukaryotes. And so although they are falling under the same branch of prokaryotes, they are very, very different from each other and they that is why they are into, these separate, domains is what they call them. And so again, as we move forward in our course, we'll be able to talk more and more about all of the, groups that are on this map. But for now, this here concludes our introduction to the members of the microbial world and I'll see you all in our next video.

Which of the following groups is composed of prokaryotic organisms?

• A. Eukarya
• B. Archaea
• C. Fungi
• D. Prions

Which of the following groups is composed of eukaryotic organisms?

• A. Protozoa
• B. Bacteria
• C. Archaea
• D. Viroids

Which of the following groups is considered acellular?

• A. Algae
• B. Helminths
• C. Bacteria
• D. Viruses

Here’s what students ask on this topic:

What are the main differences between prokaryotic and eukaryotic cells?

Prokaryotic cells, such as bacteria and archaea, lack a nucleus and membrane-bound organelles. They are generally unicellular and have a simpler structure. Their DNA is located in a nucleoid region. Eukaryotic cells, found in organisms like fungi and protists, have a defined nucleus containing their DNA and various membrane-bound organelles, such as mitochondria and the endoplasmic reticulum. Eukaryotic cells can be either unicellular or multicellular. These structural differences are crucial for their functions and roles in the microbial world.

How do viruses differ from bacteria in terms of structure and replication?

Viruses are acellular infectious agents, meaning they are not made of cells and lack cellular structures. They consist of genetic material (DNA or RNA) enclosed in a protein coat called a capsid. Some viruses also have an outer lipid envelope. Unlike bacteria, which are living prokaryotic cells that can reproduce independently through binary fission, viruses require a host cell to replicate. They hijack the host's cellular machinery to produce new viral particles, leading to the host cell's damage or death.

What are the three main types of acellular infectious agents?

The three main types of acellular infectious agents are viruses, viroids, and prions. Viruses consist of genetic material (DNA or RNA) enclosed in a protein coat. Viroids are small, circular RNA molecules that infect plants and do not encode proteins. Prions are misfolded proteins that can induce other proteins to misfold, leading to diseases such as Creutzfeldt-Jakob disease in humans. These agents are distinct from cellular organisms as they lack cellular structures and require a host for replication.

Why are bacteria and archaea considered fundamentally different despite both being prokaryotes?

Bacteria and archaea are considered fundamentally different due to significant differences in their genetic, biochemical, and structural characteristics. Bacteria have peptidoglycan in their cell walls, while archaea do not. Archaea have unique membrane lipids and their ribosomal RNA sequences differ significantly from those of bacteria. Additionally, archaea often thrive in extreme environments, such as high temperatures or high salinity, where most bacteria cannot survive. These differences justify their classification into separate domains.

What are the main groups of eukaryotic microorganisms studied in microbiology?

The main groups of eukaryotic microorganisms studied in microbiology include fungi, protists (such as algae and protozoa), and helminths. Fungi are important decomposers and can be unicellular (like yeasts) or multicellular (like molds). Protists are a diverse group that includes photosynthetic algae and heterotrophic protozoa. Helminths are parasitic worms that can cause diseases in humans and animals. These groups are studied for their ecological roles, pathogenic potential, and biotechnological applications.