Eukaryotic vs Prokaryotic Cells and Bacterial Shapes (PDF)

Introduction to Microbiology Dr I Gobe University of Botswana Dr Gobe, UB  To Cover : ◼ Differences and similarities between prokaryotic and Eukaryotic cells ◼ Common bacteria shapes and arrangements ◼ Cells wall structure of bacteria: gram...

Introduction to Microbiology Dr I Gobe University of Botswana Dr Gobe, UB  To Cover : ◼ Differences and similarities between prokaryotic and Eukaryotic cells ◼ Common bacteria shapes and arrangements ◼ Cells wall structure of bacteria: gram positive and gram negatives Dr Gobe, UB  Microbiology ◼ the study of microorganisms, with "micro" meaning small and "biology" referring to the study of living things. ◼ A microbe, or microorganism, is a microscopic organism that comprises either a single cell (unicellular); cell clusters; or multicellular, relatively complex organisms. ◼ Microbiology is the study of microscopic organisms, such as bacteria, viruses, archaea, fungi and protozoa. Dr Gobe, UB  Types of microorganisms ◼ Microorganisms are divided into seven types: bacteria, archaea, protozoa, algae, fungi, viruses, and multicellular animal parasites ( helminths ). ◼ Each type has a characteristic cellular composition, morphology and reproduction. ◼ Microorganisms are beneficial in producing oxygen, decomposing organic material, providing nutrients for plants, and maintaining human health, but some can be pathogenic and cause diseases in plants and humans. Dr Gobe, UB  Types of microorganisms ◼ Bacteria: unicellular organisms. The cells are described as prokaryotic because they lack a nucleus. ◼ Fungi (mushroom, molds, and yeasts) are eukaryotic cells (with a true nucleus). Most fungi are multicellular and their cell wall is composed of chitin ◼ Viruses are noncellular entities that consist of a nucleic acid core (DNA or RNA) surrounded by a protein coat. Although viruses are classified as microorganisms, they are not considered living organisms. ◼ Parasites: A group of eukaryotic organisms consisting of the flatworms and roundworms, which are collectively referred to as the helminths. Although they are not microorganisms by definition, since they are large enough to be easily seen with the naked eye, they live a part of their life cycle in microscopic form. Since the parasitic helminths are of clinical importance, they are often discussed along with the other groups of microbes. Dr Gobe, UB  Types of microorganisms ◼ Algae, also called cyanobacteria or blue-green algae, are unicellular or multicellular eukaryotes that obtain nourishment by photosynthesis. They live in water, damp soil, and rocks and produce oxygen and carbohydrates used by other organisms. It is believed that cyanobacteria are the origins of green land plants. ◼ Protozoa are unicellular aerobic eukaryotes. They have a nucleus, complex organelles, and obtain nourishment by absorption or ingestion through specialized structures. Dr Gobe, UB Dr Gobe, UB 3 Domains of life Dr Gobe, UB  Some Basic Classification Terms: ◼ Three Domains of life: ◼ bacteria (Prokaryotes) ◼ Archaea (Prokaryotes) ◼ Eukarya (Eukaryotes) -Us! (and all other animals) -Fungi -Protozoans -Parasites Dr Gobe, UB  Characteristics of Prokaryotic and Eukaryotic Cells ◼ Prokaryote: are always single-celled organisms, lack a defined nucleus. ◼ Eukaryote: can be single-celled or multi-cellular organisms Dr Gobe, UB Prokaryotic & Eukaryotic cells: what do they have in common? And How do they differ? Dr Gobe, UB  Characteristics Shared ◼ Perform the same basic functions ◼ Surrounded by plasma membrane to control what enters and leaves the cell ◼ “Filled” with cytoplasm ◼ Contain ribosomes to make protein ◼ Contain DNA to give the general instructions for the cell’s life Dr Gobe, UB  How are prokaryotic cells different from eukaryotic cells? ◼ Nucleus or No Nucleus: ◼ Eukaryotic DNA is in a nucleus surrounded by a nuclear membrane ◼ Prokaryotic DNA is in a nuclear region; no nuclear membrane ◼ Organization of DNA: ◼ Eukaryotic cells have paired chromosomes ◼ Prokaryotic cells have a single circular chromosome Fig. 4-3 ◼ Eukaryotic cells have histone proteins ◼ Prokaryotic cells lack histone proteins Dr Gobe, UB  How are prokaryotic cells different from eukaryotic cells? ◼ Membrane-Bound Organelles: ◼ None in prokaryotic cells! ◼ Cell Wall structure: ◼ Prokaryotic cell wall has peptidoglycan Fig. 4-3 ◼ plant and fungal cells have both cellulose and chitin ◼ Animal cells don’t have cell walls! Dr Gobe, UB How are prokaryotic cells different from eukaryotic cells? ◼ Cytoskeleton - none in prokaryotes NB: The cytoskeleton is a network of intercellular proteins fibres that help a cell with shape, support, and movement. ▪ Reproduction - Asexual in prokaryotes: binary fission - Asexual and sexual in eukaryotes; meiosis and mitosis respectively Dr Gobe, UB  Sizes of bacteria: a handy scale Fig. 3-2 Prokaryotes range from 0.5 – 2.0 µm in diameter & from 1.0 – 60 µm in length Dr Gobe, UB  What does size have to do with it? ◼ Prokaryotic cells are much smaller than eukaryotic cells. advantages? ◼ Smaller surface area to volume allows nutrients to easily and quickly reach inner parts of the cell. ◼ Eukaryotic cells are larger and can not pass nutrients as quickly. They require specialized organelles to: ◼ carry out metabolism ◼ provide energy ◼ transport chemicals throughout the cell Dr Gobe, UB  Summary of differences! Prokaryotic Cells Eukaryotic cells small cells (< 5 mm) larger cells (> 10 mm) always unicellular often multicellular no nucleus or any membrane-bound always have nucleus and other organelles membrane-bound organelles DNA is circular, without proteins DNA is linear and associated with proteins to form chromatin ribosomes are small (70S) ribosomes are large (80S) no cytoskeleton always has a cytoskeleton cell division is by binary fission cell division is by mitosis or meiosis reproduction is always asexual reproduction is asexual or sexual Dr Gobe, UB Common bacteria shapes and arrangements Dr Gobe, UB Bacteria Bacteria are unicellular organisms. prokaryotic because they lack a nucleus. have a peptidoglycan cell wall; they divide by binary fission; and they may possess flagella for motility Classification of bacteria 1. Shape major shapes: bacillus (rod shape), coccus (spherical shape), spirilla (spiral shape), and vibrio (curved shape). 2. Cell wall can be classified as either Gram-positive or Gram-negative when using the Gram staining 3. response to gaseous aerobic (living in the presence of oxygen), anaerobic (living without oxygen), and facultative anaerobes (can live in both environments). 4. Energy acquisition heterotrophs or autotrophs. Autotrophs make their own food by using the energy of sunlight or chemical reactions, in which case they are called chemoautotrophs. Heterotrophs obtain their energy by consuming other organisms. Bacteria that use decaying life forms as a source of energy are called saprophytes. Dr Gobe, UB Dr Gobe, UB  Common bacteria shapes and arrangements Dr Gobe, UB  Shape of Bacteria ◼ Cocci – spherical/ oval shaped ◼ Bacilli – rod shaped ◼ Vibrios – comma shaped ◼ Spirilla – rigid spiral forms ◼ Spirochetes – flexible spiral forms ◼ Actinomycetes – branching filamentous bacteria. Dr Gobe, UB Dr Gobe, UB Dr Gobe, UB  Arrangement of bacteria: Bacilli Coccobacilli Bacteria: Gardnerella vaginalis; or causing influenza-like Haemophilus influenzae. Chlamydia trachomatis, Diplobacilli Bacteria:Klebsiella rhinoscleromatis that causes chronic nasal infection in humans. Streptobacillus moniliformis that is the causative agent of rat-bite fever. palisade bacteria; Corynebacterium diphtheria, which is the causative agent of diphtheria Dr Gobe, UB Cocci: Round bacteria in clusters Staphylococcus aureus (5,400X)) Dr Gobe, UB Streptococci (cocci in chains) : spreptococcus pyogenes ◼ S pyogenes is the most common bacterial cause of acute pharyngitis, accounting for 15-30% of cases in children and 5-10% of cases in adults. Dr Gobe, UB Streptococcus pneumoniae appear as gram-positive diplococci. The cells are somewhat tapered at the ends giving the "lancet" shaped appearance. Pneumococcus bacteria can cause infections in many parts of the body, including Lungs (pneumonia) Ears (otitis) Sinuses (sinusitis) Brain and spinal cord tissue (meningitis) Blood (bacteremia) Dr Gobe, UB Gram-negative diplococci Gonorrhea is a sexually transmitted disease (STD) caused by infection with the Neisseria gonorrhoeae bacterium. N. gonorrhoeae infects the mucous membranes of the reproductive tract, including the cervix, uterus, and fallopian tubes in women, and the urethra in women and men. Dr Gobe, UB  Bacilli eg lactobacillus acidophilus Found in the mouth, intestine and vagina, it plays an important role in human health. produces — lactic acid help the body break down food, absorb nutrients, and fight off "bad" organisms that might cause diseases. a common probiotic that is available as a dietary supplement and is an ingredient in yogurts and other fermented foods. Dr Gobe, UB  Escherichia coli (abbreviated as E. coli) (E. coli normally live in the intestines of healthy people and animals. Most types of E. coli are harmless or cause relatively brief diarrhea. But a few strains, such as E. coli O157:H7, can cause severe stomach cramps, bloody diarrhea and vomiting. You may be exposed to E. coli from contaminated water or food — especially raw vegetables and undercooked ground beef. Healthy adults usually recover from infection with E. coli O157:H7 within a week. Young children and older adults have a greater risk of developing a life- threatening form of kidney failure. Others: Klebsiella Pneumoniae Infection; causes bacterial pneumonia, or infection in your lungs Dr Gobe, UB Questions Dr Gobe, UB