Unit 3: Bacterial Growth, Reproduction, and Genetics
This course focuses on bacteria, the most studied type of microorganism. We will begin this unit by learning how bacteria cells obtain their energy and how they grow. Metabolism varies greatly among bacteria; not all share the same kinds of mechanisms. While most require oxygen to survive, for example, some will actually die in the presence of oxygen. As the microbiology field increasingly involves the artificial cultivation of bacteria, it is important to know the methods and concepts behind their growth and cultures as well.
Bacteria divide and multiply at amazing rates. Under the right conditions, the fastest bacteria can divide every 20 minutes! That means that if you cultured just one single bacteria cell before you went to bed, you could wake up 8 hours later with a plate of more than 16 million bacteria! Much of bacterial reproduction is asexual, occurring through binary fission. In binary fission, one cell literally divides in two. We will conclude this unit by learning about horizontal gene transfer, a process by which one bacteria cell incorporates genetic changes from another cell without being its offspring. This unique feature has allowed bacteria to adapt and grow in conditions it would not otherwise be able survive. It has also led to the increase of drug-resistant bacterial infections.
Completing this unit should take you approximately 15 hours.
Upon successful completion of this unit, you will be able to:
- describe how bacteria grow and divide;
- outline methods to prevent microbial growth and how antibiotic resistance occurs;
- identify the different types of bacterial reproduction;
- explain how bacteria process, regulate, and exchange their genetic material;
- list different types of genetic mutations; and
- compare and contrast genetics and methods of reproduction in various microorganisms.
3.1: Bacterial Growth
3.1.1: Growth and Nutrition Requirements
Read this this chapter to learn about the requirements necessary for bacterial growth. Be sure to read each of the subsequent pages in the chapter.
3.1.2: Generation Time
Read this lecture about the concept of generation time. Test your knowledge with the short quiz at the bottom of the page.
3.1.3: Bacterial Growth
This chapter provides an overview of bacterial growth. Be sure to read the rest of the chapter by clicking "Chapter Continued" at the bottom of each page.
3.1.4: Estimation Methods for Population
Read this article to review the different ways bacteria can be counted.
3.1.5: Growth Control
Read this page and the following two pages. These pages discuss general microbial growth techniques: sterilization and employing physical and chemical agents. In Unit 1, you learned about the history of antimicrobial techniques, including the independent observations of Semmelweis and Nightingale.
3.2: Bacterial Reproduction
3.2.1: Asexual vs. Sexual Reproduction
Read this article to compare and contrast the differences between these two reproductive strategies. Only eukaryotes can reproduce with meiosis.
3.2.2: Binary Fission and Budding
Read these three pages. Only prokaryotes go through binary fission.
Watch this short video for a discussion of budding in yeasts.
3.2.3: Endospore Formation
Read these three pages to learn about the special circumstances under which endospores form in certain types of bacteria.
3.3: Bacterial Genetics
3.3.1: Bacterial Chromosome
Read this article to learn how bacterial chromosomes differ from eukaryotes.
3.3.2: Processing Genetic Information
Watch this animation, which shows how transcription and translation occur in bacteria. You should consider reviewing gene transcription and gene expression in prokaryotes and eukaryotes.
3.3.3: Genetic Regulatory Mechanisms
Read this page and review the diagrams in the left panel. Click on Figures 1 to 10 for a graphical explanation of operon mediated bacterial gene expression.
3.3.4: Genetic Information Exchange
Read this page. Click on Figures 1 to 4 for a graphical explanation of DNA exchange mechanisms in bacteria.
Read this chapter, which summarizes mutations that occur in the cell.
Complete this ungraded assessment. Antibiotic drugs attack both pathogenic and normal flora bacteria.
3.4:Reproduction and Genetics in other Microorganisms
Read the introduction and then move on to "Question 1" to move to the next page (Reproduction: Bacteria), and answer the question (you can check the correct answer if you click on the "Answer" button). Return to the introduction page, and click on "Next." Explore all animations and answer "Question 2." Return to "Reproduction: Bacteria" and click on "Next" to move to "Reproduction: Fungi." Explore all animations, and answer "Question 3."