Chapter 1.2 Bacteria PDF

1.2 : BACTERIA Bacteria (plural), bacterium (singular). 1 AT THE END OF THIS SUBTOPIC, YOU WILL BE ABLE TO: 1. List the basic characteristics of bacteria. 2. Identify bacterial components and its function....

1.2 : BACTERIA Bacteria (plural), bacterium (singular). 1 AT THE END OF THIS SUBTOPIC, YOU WILL BE ABLE TO: 1. List the basic characteristics of bacteria. 2. Identify bacterial components and its function. 2  BASIC CHARACTERISTICS Bacteria are prokaryotes. They can grow and multiply/ reproduce very quickly, using binary fission. They are found almost everywhere: in the air, soil, water, and inside living things, including humans. one square centimeter of human skin can harbor around 100,000 bacteria cells or even more. Some bacteria can live in extreme environments (hot springs or icy lakes). 3  BACTERIAL REPRODUCTION Each new cell is a clone of the original, with the same genetic material. This process allows bacteria to multiply quickly. 4 IMPORTANCE OF BACTERIA While some bacteria can cause diseases in humans and animals, many others are helpful. For example: Antibiotics - some bacteria produce medicines like streptomycin. Digestion - some bacteria live in our guts and help with digestion. Food - bacteria are used to make foods like yogurt, tempeh and sourdough bread. Decomposition - bacteria help break down dead plants and animals. 5  SHAPES & ARRANGEMENTS Most bacteria come in one of three basic shapes: 1. Coccus: round/ spherical/ oval-shaped 2. Bacilli: rod-shaped 3. Spiral: spiral/ corkscrew-shaped 6 COCCUS Arrangements of cocci: 7 2. ROD/ BACILLUS Arrangements of bacilli: 8 3. SPIRAL Several spiral forms: 9 BACTERIA STRUCTURE & COMPONENTS 1) Capsule 2) Cell wall 3) Cell membrane 4) Cytoplasm 5) Nucleoid 6) Flagella 7) Pili 8) Ribosomes 9) Fimbria 10) Plasmid 11) Endospore 10  capsule (kapsul) Cell wall (dinding sel) Cell membrane (membran sel) Nucleoid region (has DNA) Cytoplasm (sitoplasma) 11  BACTERIAL CELL ENVELOPE 1. Capsule - A protective layer that helps bacteria survive by preventing drying out and being attacked by other cells 2. Cell wall - Gives the bacteria its shape and protects it. 12 3) Cell membrane  Controls what goes in and out of the cell.  Protein anchor – a place to hold/ place proteins.  produce energy  Produce cell wall components  helps maintain cell shape 4) Cytoplasm  A jelly-like substance inside the cell that holds important parts like DNA and ribosomes.  Place where cell growth, metabolism, and replication processes are carried out. 13 Nucleoid bacteria do not have a membrane enclosed nucleus. Its DNA is in the cytoplasm area (known as nucleoid). The area/ region where the bacterial genetic material (DNA) is located. It is the control center of the cell. 14 Nucleoid Nucleoid is not a nucleus. It is an area in the cytoplasm. Bacteria usually have only one circular DNA molecule. However, some bacteria species can produce DNA plasmid (DNA that is not part of nucleoid). 15 16 RIBOSOMES Protein factory (produce proteins). Spherical-shaped. Very small, can only be seen using electron microscope. 17 FLAGELLA Flagella (singular, flagellum) are hair like structures that provide a means of locomotion/ movement). beat in a propeller-like motion to help the bacterium move toward nutrients; away from toxic chemicals Flagella have different numbers and arrangements: 18 (a) monotrichous (single flagellum at one end). (b) amphitrichous (either single or tufts flagellum at both ends of the cell) (c) Lophotrichous (with tuft or cluster of flagella at one ends) (d) And (e) Peritrichous (flagella distributed all over) 19 20  FIMBRIAE & PILI (singular: fimbria) (singular: pilus)  assist bacteria to attach/ hold to  Functions: other cells or surfaces, such as teeth, a) DNA transfer intestines, and rocks.  Via conjugation (temporary union of 2 bacterial cells where one transfers  A cell can have from several up to part or all of its genome to the other). hundred per cell.  Sex pili/ conjugation pili b) Motility/ movement  Only one or two per cell.  Pili is usually longer than fimbria. 21 Electron micrograph of an E. coli (14,300X).  The short fimbriae are used for attachment to surfaces.  The long pili is used for DNA transfer. 22 Plasmid is DNA that is NOT part of the main DNA. Plasmid is small & in circular shape. Not all bacteria can produce plasmids. Plasmid codes for (have information to produce) proteins that are not coded by the main DNA (in the nucleoid region). For example, some plasmid have genes to produce antibiotic resistance. 23 24 Endospore Are dormant (resting/ inactive) survival form of bacteria. NOT a reproductive structure (bacterial endospore is not the same as fungal spore). Under conditions of starvation, bacteria will produce a single endospore (sporulation process). very resistant to high temperatures, most disinfectants, low energy radiation, drying, etc. Some endospore can survive for several decades. 25 26  When the surrounding environment is suitable again for bacteria to grow, germination will happen. *Germination = endospores develop into functional vegetative bacterial cells Not all bacteria can produce endospore. Example of endospore producing bacteria: Bacillus & Clostridium. 27 28