Topic: Bacteria

Target group

5th‑grade students of elementary school

Core Curriculum

5 ) explains the importance of bacteria in nature and for humans.

General aim of education

Students describe the bacteria, the place where they occur and the meaning.

Key competences

• communication in foreign languages;

• digital competence;

• learning to learn.

Criteria for success
The student will learn:

• describe the locations of bacteria;

• describe the life activities of bacteria;

• present the positive and negative significance of bacteria.

Methods/techniques

• expository

  • talk.

• activating

  • discussion.

• programmed

  • with computer;

  • with e‑textbook.

• practical

  • exercices concerned.

Forms of work

• individual activity;

• activity in pairs;

• activity in groups;

• collective activity.

Teaching aids

• e‑textbook;

• notebook and crayons/felt‑tip pens;

• interactive whiteboard, tablets/computers;

• blocks of self‑adhesive sheets;

• plasticine or other plastic mass;

• ruler.

Lesson plan overview

Before classes

• Students get acquainted with the content of the abstract. They prepare to work on the lesson in such a way to be able to summarize the material read in their own words and solve the tasks themselves.

Introduction

• The teacher gives the topic, the goals of the lesson in a language understandable for the student, and the criteria of success.

• The teacher instructs students to look at the illustration of „Clusters of bacteria grown in the laboratory”. He discusses the method of establishing a bacterial culture and explains what is their food. He asks the pupils to indicate the individual bacteria in the illustration and describe their appearance, and then define the term „microorganisms”.

• The teacher displays an interactive illustration. Students discuss the characteristics of a bacterial cell.

Realization

• Students read the fragment Fri „Diversity of bacteria” and then perform interactive exercise No. 1. The teacher asks them to remember the names of three characteristic shapes of bacteria, and then they made them from plasticine (or other plastic mass).

• The teacher asks students to read the fragment of the abstract entitled „Bacteria habitat” and try to remember its content. Then the participants, working in pairs, ask each other about the knowledge of the fragment.

• The teacher asks students to carry out the interactive exercise No. 2 themselves.

• The teacher asks what it means to say that the bacteria are heterotrophic. Then he instructs the students to look for ways of eating the intestinal nutrition of bacteria in the abstract.

• Students analyze the „Temperature effect on bacterial activity” illustration. Then answer the questions:

  • Under what conditions are bacteria reproducing and absorb the most food?

  • How does the temperature above 60 ° C affect bacteria?

  • Why is bed linen washed at 60 ° C and above?

  • Why should you cook or fry meat before eating?

  • Why do I need to pour boiling water on a daily dishwashing sponge?

  • How does bacteria affect a temperature of less than 5 ° C?

  • Why do we store food in the fridge?

• Students read the fragment Fri „Multiplication of bacteria”.

• The teacher divides the students into groups. Each team receives a small block of self‑adhesive sheets. The teacher explains that the block is a bacterial cell model that will reproduce. He asks his pupils to define the way in which the bacteria multiply and the conditions in which the process takes place. After answering by the students, the teacher demonstrates the first division of bacteria (divides the block into 2 parts) and says that it resulted in two daughter cells. He instructs the charges to divide their block in half and repeat this step until obtaining individual sheets. Each group appoints two people, one of which counts the following divisions of the bacterial model, the second determines the time of cell division (it should be assumed that the division takes place every 20 minutes). The teacher asks students how many bacteria will be formed from one cell after three hours.

Summary

• The teacher briefly presents the most important issues discussed in class. He answers the additional questions of the proteges and explains all their doubts. Students complete notes.

Homework

• Make at home a note from the lesson using the sketchnoting method.

• Listen to the abstract recording at home. Pay attention to pronunciation, accent and intonation. Learn to pronounce the words learned during the lesson.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Bacteria

Without a great exaggeration it can be said that bacteria are present everywhere: in water, soil and air. Due to their microscopic size they are easily transported by air currents on dust grains or in drops of water. Each bacterial species has its specific requirements concerning a medium type, ambient temperature and access to oxygen. Many bacteria live on a surface or inside of other organisms, because of favorable conditions of temperature and humidity, and sufficient amount of food available to them.

Bacteria are the smallest, single‑celled organisms on Earth. Their size is within a range from 0.2 µm to 10 µm. If the bacterial cells were arranged in a row, then 1 mm would contain about 1000 of them. Some bacterial species form colonies, in which individual cells remain connected to one another with their cell walls or slime layer after a division. When a bacterium separates from the colony, it can function as an individual single‑celled organism and start a new colony.

The bacterial cells can have different shapes, from which their names often come. They include spherical cocci, elongated bacilli and spiral vibrios, spirilla, and spirochaeta. Cocci can be arranged, so called diplococci. Sarcina form regular packs, staphylococci associate into irregular grapelike clusters, while streptococci are arranged into bead‑like chains. The cellular shapes and the morphology of a colony are features characteristic for a specific bacterial species.

Despite their small size and a body formed of just one cell, the bacteria performs all life functions. They feed, respire, excrete, reproduce and grow, and are sensitive to the environmental conditions.

The majority of bacteria are heterotrophs and use nutritional substances from their environment. They include saprobionts feeding off dead organic matter. They excrete digestive enzymes into the medium, and absorb with a whole surface of their bodies substances digested outside. This way, the soil bacteria decompose animal feces and their bodies, or plant remains. Dental bacteria, feeding off food residues remaining in the oral cavity after a meal, lactic acid bacteria causing milk fermentation and pickling of vegetables, and those responsible for food spoilage, function in a similar way.

Many bacteria species are parasites exploiting other organisms. They enter their bodies by an oral route together with eaten food or drank water, by a respiratory route with breathed air, or through wounds. In the case of plants, they usually penetrate through damaged tissues, causing infectious diseases.

Similarly to all other organisms, the bacteria release the energy required for life in the process of cellular respiration. Those leaving in the environment rich in oxygen use aerobic respiration, breaking down organic compounds to carbon dioxide and water. Bacterial species living in environments lacking or poor in oxygen produce energy without this element. A process of anaerobic respiration using sugar as a source of energy is called fermentation. When protein is used as a source of energy, then the process of decay occurs.

Bacteria reproduce mainly through cellular division and budding. In favorable conditions of a temperature and humidity, and a sufficient access to food, bacteria multiply very fast, and their numbers can double ca. every 20 minutes. Fortunately, this process is not endless. A lack of food and the accumulation of toxic waste products inhibits the colony growth. In consequence, the number of live individuals decreases.

In unfavorable conditions, such as drought, a high or low temperature, pressure oscillations, or a presence of bactericides, bacteria stop treproducing and pass into the dormant stage. They lose water, shrink and remain dormant until the conditions improve. Some species form endospores. These are very resistant forms of cells showing no detectable metabolism, which germinate (even after several dozen years) when conditions are favorable.

All environments function due to bacteria. If the soil bacteria disappeared suddenly, the whole Earth would be covered with enormous amounts of dead plants and animals, and mineral substances in the soil would be exhausted. Bacteria together with fungi and certain protists decompose the dead organic matter, releasing elements and simple organic compounds from it. This way these substances can be absorbed by plants and built into their bodies. The plant material eaten by consumers becomes a part of their bodies. After their death, the organic compounds once again become food for microorganisms. This way, bacteria and other saprobionts facilitate matter circulation in the environment.

Bacteria forming nodules on roots of Fabaceae plants, such as peas, help these plants to absorb mineral substances from their environment. Bacterial cooperation with herbivores enables digestion of cellulose, the main component of plant food. Various bacterial species are present on and in the human body, and the majority of them are symbiotic organisms, having a beneficial function. Only some of them are pathogens. One of the most common species is Escherichia coli, found in the large intestine. It helps to digest food and produces certain vitamins. However, in specific conditions it can cause dangerous diseases: urinary tract infections, neonatal meningitis, or gastroenteritis.

In specific circumstances, bacteria can also be harmful. Pathogenic bacteria are parasites weakening an infected organism by destroying its tissues or excreting poisons, so‑called toxins. Saprobiontic bacteria cause rotting and decay of wooden structures, and food spoilage at households. Their excessive multiplication results in contamination of water reservoirs.

• Bacteria live in all environments on the Earth: in water, soil, or air, and inside other organisms.

• Majority of bacteria are heterotrophs, but there are also some autotrophic bacteria.

• Heterotrophic bacteria include saprobionts, parasites and symbionts.

• Bacteria use processes of aerobic or anaerobic respiration, and reproduce by cell division.

• They play an important role in the natural environment, decomposing dead organic matter, and they are used in many areas of human life.