Bacteria and fungi.pdf

Bacteria & Fungi Lab 04 Learning objectives: - Understand what is meant by prokaryotic cell. List the key features of bacterial cell Describe the structure of a typical bacterial cell Identify the fungi phyla Provide definitions for the key terms given below. Key Terms Bacteria; cell wall; chromos...

Bacteria & Fungi Lab 04 Learning objectives: - Understand what is meant by prokaryotic cell. List the key features of bacterial cell Describe the structure of a typical bacterial cell Identify the fungi phyla Provide definitions for the key terms given below. Key Terms Bacteria; cell wall; chromosome, coccus; cytoplasm; flagellum; plasma membrane; prokaryote; ribosome; spore bacillus; capsule, fungi, yeast, mould. An Outline of Prokaryotic Cell Prokaryotic organisms are the most ancient and widespread forms of life. They are single-called organisms that belong to the kingdom Monera. The term “ prokaryotes” means before the nucleus” and this cell type is regarded as relatively simple. Bacteria are considered as prokaryotic organisms. Many of the Bacteria are well known for their role in causing infectious disease. Other species of Bacteria perform important functions in decomposing and the recycling of nutrients. Some Bacteria are used in industrial processes for the production of foods and other materials. In spite of their small size, which is typically a length or diameter of 1 to 10 !m Bacterial cells share a number of properties (figure 1): - There is no membrane-bound nucleus enclosing the genome. - They lack of other membrane-bound organelles, in addition to the nucleus. - They usually possess just a single circular molecule of double-stranded DNA as chromosome, through other smaller DNA molecules called plasmids may be present. - They are, with few exceptions, surrounded by a cell wall. - They divide by process known as binary fission (literally meaning ‘ splitting into two’). General BiologyFigure 1 illustrates the different parts of the bacterial cell BIO 101 Bacteria & Fungi Lab 04 Bacterial cells can vary in their cell shape; they may be round (cocci), rod-shaped (bacilli), comma shaped, or even spiral (figure 2). Figure 2. Bacterial cell shape Some bacteria produce spores, which can survive unfavourable conditions such as desiccation and high temperatures. The spores are dormant, and they will only germinate to produce cells when the appropriate conditions are resorted. Some spores, called endospores, form within the cell and they are unique to bacteria. Endospores are thick-walled and can survive under very harsh condition (figure 3). Figure 3. Endospore-forming bacilli. Endospores are dehydrated, retractile cells appearing as points of bright light under phase contrast microscopy. Fungi Fungi include yeasts (one-called), and mushrooms and moulds (multi-called). Unlike plants, fungi do not make their own food. Some species of fungi get their nutrition by breaking down remains of dead plants or animals. Others are parasites. Here we discuss yeasts and moulds – mushrooms are regarded as higher fungi. Yeasts: Yeasts belong to the kingdom of Fungi. The main division of fungi are: Phytomycetes, Ascomycetes, Basidiomycetes. The yeasts, such as the baking yeast Sachromyces cervisiae belong to Ascomycetes. Common mushrooms belong to Basidomycetes. General Biology BIO 101 Bacteria & Fungi Lab 04 Figure: left is Sachromyces cervisiae under a microscope; right is yeast structure. Blue cheese Moulds Moulds are microscopic fungi that live on plant or animal matter. They grow as single filaments that can branch together making a strongly knit structure like mat that can often be seen with the naked eye. Left: Electron microscope image of Penicellium; Right: Surface mould on an orange. General Biology BIO 101 Bacteria & Fungi Lab 04 In many moulds, the body consists of: - root threads that invade the food it lives on, - a stalk rising above food, - spores that form at the ends of the stalks Usually they look fluffy, being a familiar sight on foods like gam, cheese and bread. They multiply by producing clusters of dry spores; these spores can be transported by air, water, or insects. Moulds most often found on meat and poultry are , penicillium. Penicillium Aspergillus Please download from: https://drive.google.com/open?id=0BwTUWl9nXHdDdHVYZ3JMa2JJSk0 General Biology BIO 101