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Exploring the structure of bacteria and their diverse roles in the environment and human health.
Did you know that right now, you are carrying around roughly 3 pounds of bacteria—about the same weight as your human brain?
Bacteria are prokaryotes, meaning they are simple, single-celled organisms that lack a nucleus. Instead of a 'control center,' their DNA floats freely in the cytoplasm. Most bacteria fall into three categories based on their shape: Cocci (spheres), Bacilli (rods), and Spirilla (spirals). To survive, they use a rigid cell wall for protection and sometimes a whip-like tail called a flagellum to swim through fluids.
Imagine you are looking through a microscope at a water sample: 1. You see tiny round balls clustered like grapes. These are Cocci. 2. You see long, pill-shaped structures. These are Bacilli. 3. You see wavy, corkscrew-like threads. These are Spirilla.
Quick Check
If a scientist discovers a new bacterium that looks like a tiny sausage, which shape category does it belong to?
Answer
Bacilli (rod-shaped).
Not all bacteria are 'germs.' In fact, most are helpful! Your microbiome is a community of 'friendly' bacteria in your gut that helps you digest food and produce vitamins. Bacteria are also the world's best recyclers, breaking down dead plants and animals to return nutrients to the soil. However, some bacteria are pathogens. These 'foes' cause diseases like strep throat or food poisoning by releasing toxins that damage your cells.
Bacteria are essential in food production. To make yogurt: 1. Specific bacteria (Lactobacillus) are added to milk. 2. They eat the milk sugars and produce lactic acid. 3. The acid changes the milk proteins, making it thick and tangy. This is a 'friendly' use of bacteria!
Quick Check
What is the primary difference between a 'friendly' bacterium and a 'pathogen'?
Answer
Friendly bacteria provide benefits like digestion or decomposition, while pathogens cause disease and harm the host.
Bacteria don't need a partner to reproduce; they use a process called binary fission. This is a form of asexual reproduction where one cell clones its DNA and splits into two identical 'daughter' cells. This process is incredibly fast. Under ideal conditions, some bacteria can divide every 20 minutes. This leads to exponential growth, where the population doubles at a constant rate.
Let's calculate how many bacteria grow from a single cell in one hour if they divide every 20 minutes. 1. Use the formula for exponential growth: , where is the number of generations. 2. In 60 minutes, there are generations. 3. Calculate: cells. 4. If this continued for 24 hours, there would be more bacteria than people on Earth!
Which bacterial structure is used specifically for movement?
If a bacterial population starts with 1 cell and undergoes 4 rounds of binary fission, how many cells will there be?
All bacteria are pathogens that cause disease in humans.
Review Tomorrow
In 24 hours, try to sketch the three main shapes of bacteria from memory and label them (Cocci, Bacilli, Spirilla).
Practice Activity
Look at the ingredients on a yogurt container or a probiotic drink. Can you find the names of any 'friendly' bacteria listed?