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UNIT 1: THE MICROBIAL WORLD 2 major structures of classes of cells Prokaryotic -found in the domains of Bacteri...

UNIT 1: THE MICROBIAL WORLD 2 major structures of classes of cells Prokaryotic -found in the domains of Bacteria and Archaea WHAT IS MICROORGANISMS -lack nucleus and organelles. -circular chromosomes Also called microbes, are life forms too small to be seen by the naked eye. They can live and eat almost everything, they can live in nearly every kind of environment (including water) at the temperature of 750 F. Many microbes are single celled, some can form complex structures, and some are multicellular. Earth (Home to 1 trillion Microbial species) 0.001 % have been discovered Oldest microbes (cyanobacteria) live in microbial communities Eukaryotic - found in the domain Eukarya Microbiology - fungi algae, protozoa - the study of the dominant form of life on earth. - have organelles (assortment membrane-enclosed cytoplasmic structures) Microscopic techniques - linear chromosomes within the nucleus Culture (collection cells grow nutrient medium) Medium (plural media, can be liquid (broth) or solid (agar, nutrient agar) Growth (the increase of number of microorganisms) Colony (consists of millions of cell on a solid nutrient) 1.2 STRUCTURES AND ACTIVITIES OF MICROBIAL CELLS All cells have the ff. Cytoplasmic (cell/plasma) membrane (permeability barrier) Cytoplasm (aqueous mixtures of different macromolecules (proteins, lipids, nucleic acids, and Genes, Genomes, Nucleus,and Nucleoid polysaccharides) ) Ribosomes (protein synthesis) Genome Cell wall (structural strength, only in plants cells) - full set of genes, the blueprint of organisms Bacteria doesn't have any nuclear envelope Gene - segment of DNA that encodes protein or RNA 3 Phylogenetic Domains molecules. - Bacteria - Archaea Nucleus - Eukarya - can only be found in eukaryotic cells - where DNA can be found MB441 - 1MICRO1 | MENDOZA & ZOLETA 1 University of Santo Tomas - College of Science Nucleoid - chromosomes are aggregated within the prokaryotic 1.3 MICROORGANISMS AND THE BIOSPHERE cell to form the Nucleoid. Brief History of Life on Earth Most prokaryotes have only single chromosomes, but some contains one or more small circles of DNA called the plasmids Microbes are the oldest form of life on Earth. (contains genes that are not essential and confer some special Earth is about 4.6 billion years old. property) First microbial cells appeared between 3.8 and 4.3 billion years ago The genomes of Bacteria and Archaea are typically small The first 2 billion years the atmosphere was anoxic between 500 and 10,000 genes encoded by 0.5 to 10 million (absent of O2) and only N, CO2 are present base pairs. Only microorganisms capable of anaerobic metabolisms (metabolism that do not require O2) ACTIVITIES OF MICROBIAL CELLS Evolution of phototrophic microorganisms appeared within 1 billion years of the formation of earth. Properties of ALL cells First phototrophs were anoxygenic (non-producing oxygen) such as the purple sulfur and green sulfur bacteria. Cyanobacteria (oxygenic phototrophs) appeared The early phototrophs live in microbial mats After the oxygenation multi cellular begin to form The common ancestor is the Last Universal Common Ancestor (LUCA) Properties of SOME Cells MICROBIAL ABUNDANCE AND ACTIVITY IN THE BIOSPHERE Estimated microbial cells is 2 x 1030 on earth MB441 - 1MICRO1 | MENDOZA & ZOLETA 2 University of Santo Tomas - College of Science  Microbes are even abundant in habits that are much Microorganisms as Agent of Disease too harsh for other form of life such microorganisms is Beginning of the 12 Century the major causes of called EXTREMOPHILES human death were infectious diseases caused by bacteria and viral pathogens. Organisms listed are the current “record holders” for growth in laboratory culture at extreme conditions listed. Anaerobe showing growth at 122°C only under several atmospheres of pressure. Microorganisms, Agriculture and Human Nutrition The permafrost bacterium Planococcus halocryophilus can grow at -15°C and metabolize at Agriculture benefits from the cycling of key plant -25°C. However, the organism grows optimally at nutrients by microorganisms. 25°C and grows up to 37°C and thus is not a true Nitrogen fixation process of bacteria converts psychrophile. atmospheric nitrogen to NH3 (ammonia). P. oshimae is also a thermophile, growing optimally at NH3 is the major nutrient found in fertilizer and used 60°C. as a nitrogen source for plant growth. N. gregoryi is also an extreme halophile, growing Rumen a microbial ecosystem which microbial optimally at 20% NaCl. communities digest and ferment the polysaccharide M. yayanosii is also a psychrophile, growing optimally cellulose (the major component of plant cell wall) near 4°C. Many domesticated and wild herbivores mammals including deer, bison, camels, giraffes, and goats are 1.4. THE IMPACT OF MICROORGANISMS ON HUMAN ruminants. SOCIETY Microorganisms and Food Microbial growth can cause food spoilage and foodborne disease. The manner in which we harvest MB441 - 1MICRO1 | MENDOZA & ZOLETA 3 University of Santo Tomas - College of Science  and store food (canning, refrigeration, drying, salting Microbes often grow on submerged surfaces forming etc.) biofilms (when they grow in pipes and drains can Microbes are used for the improvement of food safety cause fouling and blockages in factory settings and and to preserve foods. pipelines, in sewers, and even in water distribution Cheese, yogurts, and buttermilk are all produce by systems). microbial fermentation of dairy products Lactic acid improves food shelf life and prevents the growths of foodborne pathogens Lactic acid- producing bacteria are used to produce a variety of sour-tasting foods (sauerkraut, kimchi, pickles and certain sausages). Even chocolate and coffee rely on microbial fermentation. Fermentative activities of yeast are essential for baking (by generating CO2 to raise dough) and for alcoholic beverages Microbial fermentation affects the flavor and taste of food and can prevent spoilage. II. MICROSCOPY AND THE ORIGINS OF MICROBIOLOGY 1.7 LIGHT MICROSCOPY AND THE DISCOVERY OF MICROORGANISMS Robert Hooke published Micrographia (in 1665 a book containing microscoping observation). Illustrated many microscoping images including fruiting structures of molds (the first known description of microorganisms) Antonie van Leeuwenhoek the first person to see Microorganism and Industry bacteria. He constructed extremely simple microscopes containing a single lens to examine Industrial Microbiology focused on the use of various natural substances for microorganisms. microorganisms as tools for major industries or Leeuwenhoek discovered bacteria in 1676 while pharmaceuticals and brewing. studying pepper-water infusions and reported to one Fermentors naturally occurring microorganisms are of his series of letters to the Royal Society of London. grown on a massive scale in bioreactors to make Leeuwenhoek described one of the bacteria from a large amounts of products (antibiotics, enzymes, pond as wee animalcules. His microscope was a alcohols and certain chemical at low cost) light microscope. Biotechnology employs genetically engineered microorganisms to synthesize products of high commercial value such as insulin or other human proteins on a small scale. Microorganisms can also be used to produce biofuels such as natural gas (methane), a product of anaerobic metabolism of methanogenic. Ethyl alcohol (ethanol) is a major fuel supplement produced by microbial fermentation of glucose. MB441 - 1MICRO1 | MENDOZA & ZOLETA 4 University of Santo Tomas - College of Science  Gram stains are an important differential staining in microbiology. Bacteria can be divided into 2 major groups; Gram Positive (appears purple-violet, thick peptidoglycan/murein) and Gram negative (appear as Pink-Red, more dangerous, thin peptidoglycan/murein). The color difference in the Gram stain arises because of the difference in the cell wall structure in gram (+) and gram (-). Magnification describes the capacity of a microscope to enlarge an image. Resolution ability to distinguish two adjacent objects as distinct and separate. Several types of light microscopy are now available (bright-field, phase contrast, differential interference contrast, dark-field, and fluorescence) Compound light microscope contains two types of lenses (objective and ocular) III. MICROBIAL CULTIVATION EXPANDS THE HORIZON OF MICROBIOLOGY 1.8 IMPROVING CONTRAST IN LIGHT MICROSCOPY Aseptic technique practice that allows for Staining Cells for Microscopic Observation preparation and maintenance of sterile nutrient media and solution. Pure cultures cells from only a single type of microorganism. Enrichment culture techniques allow for the isolation from nature of microbes having particular metabolic characteristics. 1.9 PASTEUR AND SPONTANEOUS GENERATION Spontaneous Generation Spontaneous Generation belief that life arose spontaneously from nonliving materials. Dyes can be used to stain cells and increase their Pasteur and his development of vaccines for the contrast for it to be easy and identify on a bright field disease of anthrax, fowl cholera, and rabies microscope. Pasteur's work on rabies was his most famous Basic Dyes (Methylene blue, crystal violet and success, culminating in July 1885 to a french boy safranin) name Joseph Meister. VIAS (Violet Iodine Acetone Safranin) Pasteur not only were significant in their own right but helped to solidify the concept of the germ theory of DIFFERENTIAL STAIN: THE GRAM STAIN disease. Differential stains render different kinds of cells from different colors MB441 - 1MICRO1 | MENDOZA & ZOLETA 5 University of Santo Tomas - College of Science Spontaneous Generation These discoveries also led to the development of success for the prevention and cure of many of these diseases greatly improving the scientific basis of clinical medicine and human health and welfare. Koch, Pure Cultures, and Microbial Taxonomy Koch observed that when a solid surface was incubated in air, masses of microbial cells called colonies developed each having a characteristic shape and color. He inferred that each colony had arisen from a single bacterial cell that had grown to yield the mass of cells. RIchard Petri,an associate of Koch, developed the 1.10 KOCH, INFECTIOUS DISEASE AND PURE transparent double-sided “Petri dish”: in 1887 and CULTURES quickly became the standard tool for obtaining pure culture. Ignaz Semmelweis promoted sanitary methods including hand washing as a method for preventing Koch and Tuberculosis infections. The work of Pasteur and Lister provided strong Bacteria that cause tuberculosis, Mycobacterium evidence that microbes were the cause of infection. tuberculosis, are very difficult to stain because they but it was not until the work of Robert Koch that the contain large amounts of wax-like lipid in their cell germ theory of infectious disease had direct walls. experimental support. He used Guinea pigs can be readily infected with M. tuberculosis and eventually succumb to systemic The Germ Theory of Disease and Koch’s Postulates tuberculosis. Koch showed that tuberculosis guinea pigs contained masses of M. tuberculosis cells in their Koch studies anthrax, a disease of cattle and lungs and that pure cultures obtained from such occasional of humans animals transmitted the disease to healthy animals. Anthrax is caused by the bacterium Bacillus He was awarded the 1905 Nobel Prize for Physiology anthracis. or Medicine. Koch had many other triumphs in the growing field of infectious diseases, including the discovery of the causative agent of cholera (the bacterium Vibrio cholerae) and the development of a method to diagnose tuberculosis. 1.11 DISCOVERY OF MICROBIAL DIVERSITY Sergei Winogradsky and Chemolithotrophy Koch used mice as experimental animals He was interested in bacteria that cycle nitrogen and Koch demonstrated that when a small drop of blood sulfur compounds such as nitrifying bacteria and from a mouse with anthrax was injected to a healthy the sulfur bacteria. mouse, the latter quickly developed the anthrax. He studied Beggiatoa (large sulfur oxidizing bacteria He took blood from this second animal, injected it into found in marine sediments). another, and again observed the characteristic Winogradsky was the first to define disease symptoms. He discovered that the anthrax Chemolithotrophy, which is any metabolic process in bacteria could be grown in a nutrient medium outside which energy for growth is produced using only the host. inorganic chemical compounds. MB441 - 1MICRO1 | MENDOZA & ZOLETA 6 University of Santo Tomas - College of Science  Winogradsky also revealed that these Griffith worked with a virulent strain of Streptococcus chemolithotrophic bacteria obtain their carbon from pneumoniae, a cause of bacteria in both humans and CO2 much like plants though they get their energy mice. Strain S, produced a polysaccharide coat that caused from chemical reactions rather than from light. cells to form smooth colonies on agar media and He shows these organisms which he called lithotrophs conferred the ability to kill infected mice. (stone eaters). Strain R lacked this polysaccharide and produced rough colonies that did not cause disease Martinus Beijerinck, the Enrichment Culture and Nitrogen Fixation. Avery-MacLeod-McCarty experiment shows that this transforming principle was DNA. They treated the dead remains cells of strain s with chemicals and Greatest Contribution to the field of microbiology was enzymes that destroyed protein and left behind only his clear formulation of the enrichment culture DNA. technique. They repeated Griffith's experiment with the pure DNA Clostridium Pasteurianum become first to of strains S and showed that this DNA was sufficient demonstrate the process of nitrogen fixation. to cause transformation, causing strain R cells to Beijerinck used a similar technique shortly thereafter become S-type cells and virulent. to isolate the first aerobic nitrogen-fixation bacterium, The structure of DNA was ultimately solved by James Azotobacter. D. Watsons and Francis Crick using X-ray diffraction Winogradsky isolated the first nitrifying bacteria using images of DNA taken by their colleague Rosalind an enrichment medium that contained ammonium Franklin. salts and CO2 since these chemolithotrophic bacteria They revealed that DNA is composed of a double oxidize ammonium as an energy source and are helix containing four nitrogenous bases. Guanine, autotrophic. cytosine, adenine and thymine. Beijerinck was the first to isolate sulfur-cycling 1.13 WOOSE AND THE TREE OF LIFE bacteria such as sulfate- reducing bacteria and sulfur-oxidizing bacteria, fermentative bacteria such Woese recognized that genes encoding rRNAs are as the lactic acid bacteria, and many other excellent candidates for phylogenetic analysis physiological types of bacteria as well as microbial because they are (universally distributed, functionally eukaryotes such as green algae. constant, highly conserved and adequate length to provide a deep view of evolutionary relationships. IV. MOLECULAR BIOLOGY AND THE UNITY AND Phylogenetic tree diagram depicts the evolutionary DIVERSITY OF LIFE history of the phylogeny of all cells and clearly reveals the three domains. 1.12 MOLECULAR BASIS OF LIFE Cracking code of life 1.14 AN INTRODUCTION TO MICROBIAL LIFE BACTERIA have prokaryotic cell structure undifferentiated single cells with a length that ranges from 1 to 10 micrometer. MB441 - 1MICRO1 | MENDOZA & ZOLETA 7 University of Santo Tomas - College of Science  The smallest bacteria are no more than 0.015-0.2 Different kinds of Coccus micrometers in diameter and the largest can be as Diplococci - (duo) much as 700 micrometers. Staphylococcus - (grape like structures) four phyla: Actinobacteria, Firmicutes, Streptococcus - (chain) Proteobacteria, and Bacteroidetes. Sarcina -(cubes) Different kinds of Rods UNIT 2: MICROBIAL CELL STRUCTURE AND Chains of bacilli (chain of different bacillus) FUNCTION Flagellum rods Spare-former MAJOR MORPHOLOGIES OF PROKARYOTIC CELLS MORPHOLOGIES OF PROKARYOTIC CELLS MORPHOLOGY EXPLANATION Coccus (Cocci) A cell that is spherical or ovoid in morphology. Some cocci form long chains (e.g. the bacterium Streptococcus), others occur in three-dimensional cubes (Sarcina), and still others in grapelike clusters (Staphylococcus) COMMON BACTERIAL STRUCTURES Rod or Bacillus cylindrically shaped Bacteria COMMON BACTERIAL STRUCTURES Spirillum (Spirilla) curved or loose spiral shaped STRUCTURES EXPLANATION Bacteria Plasma Membrane selectively permeable barrier, swimming motility in viscous transport, location of metabolic environments processes (respiration and Spirochetes tightly coiled Bacteria and mostly are photosynthesis), and cues for water living chemotaxis exploits swimming motility in viscous it surrounds the cytoplasm–the environment mixture of macromolecules and smaller molecules from the outside Budding and they form extensions of their cells as environment Appendaged long tubes or stalks Gas Vacuole it provides buoyancy for the bacteria maximizes nutrient uptake for and only found in some bacteria survival in nutrient-limiting conditions Ribosomes it is responsible for protein synthesis Filamentous forms they long, thin cells or chains Nucleoid the location where the DNA is found of cells and facilitates gliding motility along a surface Inclusion It is responsible for storage movement MB441 - 1MICRO1 | MENDOZA & ZOLETA 8 University of Santo Tomas - College of Science  Periplasmic space it is responsible for nutrient uptake and processing and can be definitely found in gram (-) bacteria Cell Wall responsible for protection (from pressure) and maintains the cell shape and otherly known as peptidoglycan or murein THE BACTERIAL CYTOPLASMIC MEMBRANE Cytoplasmic Membrane is a phospholipid bilayer containing embedded proteins. 2.4: BACTERIAL CELL WALLS: PEPTIDOGLYCAN Amphipathic are composed of both hydrophobic (water-repelling) and hydrophilic (water-attracting) components. Cells of Bacteria can be divided into major groups, Hydrophobic represent the tail, while hydrophilic gram-positive and gram-negative. represent the head groups. STRUCTURE OF PEPTIDOGLYCAN Hydrophobic component consists of fatty acids, while the hydrophilic component consists of a glycerol The walls of cells of Bacteria contain a rigid molecule containing phosphate and other several polysaccharide called peptidoglycan that confers functional groups (sugars, ethanolamine, or choline). structural strength on the cell. The fatty acids point inward toward each other to form It is present in all Bacteria that contain a cell wall, but the hydrophobic region, while the hydrophilic portion is not in Archaea or Eukarya. exposed to the environment or cytoplasm. It is composed of alternating repeats of two modified The lipid bilayer or a unit membrane because each glucose residues: N-acetylglucosamine (G) and phospholipid leaf forms half of the unit. N-acetylmuramic acid (M) along with the amino acids (L-alanine, D-alanine, D-glutamic acid, and Hopanoids either L-lysine or diaminopimelic acid or DPA). Physically-weak cytoplasmic membranes of some Bacteria are strengthened by sterol-like molecules PEPTIDOGLYCAN IN GRAM (+) AND GRAM (-) called hopanoids. Gram (+) has interbridges, while Gram (-) has no Integral interbridges. Integral Membranes are proteins significantly The peptidoglycan can be destroyed by lysozyme. embedded in the membrane. Peptidoglycan is a Bacteria’s major defense against It can be the channel for molecules. bacterial infection. Glycosidic Bonds is the peptidoglycan strength Peripheral around the circumference of the cell. Peripheral Membranes are more loosely attached. Peptide Bonds is the strength along the axis of the It has lipoproteins that contain a hydrophobic lipid tail cell. that anchors the protein into the membrane. It typically interacts with integral membrane proteins in Gram Positive (+) Cell Wall important cellular processes such as energy Thick cell walls are composed of the gram positive metabolism and transport. (+). It is composed of up to 90% peptidoglycan. In gram staining, the color of gram-positive (+) is purple/violet. Teichoic provides rigidity and flexibility to the cell wall. MB441 - 1MICRO1 | MENDOZA & ZOLETA 9 University of Santo Tomas - College of Science  Lipoteichoic is the covalent bond of membrane Many Bacteria and Archaea secrete sticky or slimy bonds. material on their cell surface that can contain polysaccharides or protein, however they are not part of the cell wall. Gram Negative (-) Cell Wall We term them “capsule” and “slime layer.” Thin cell walls are composed of the gram negative (-). CAPSULE AND SLIME LAYERS It is composed of up to 5% - 10% peptidoglycan. In gram staining, the color of gram positive (+) is CAPSULE pink/red. We describe this layer when the layer is organized in Polysaccharides have conformity bounds to lipid a tight matrix that excludes small particles and is (fats). tightly attached. Slime Layers is what we call when the layer is more ADDITIONAL INFORMATIONS: easily deformed and loosely attached. Capsule protects bacteria from desiccation in periods Example Microorganisms of No Cell Walls of dryness. Surface polysaccharide assists in the attachment of Mycoplasma microorganisms to solid surfaces. The binding is often ○ group of pathogenic bacteria related to facilitated by bacterial cell surface polysaccharides. gram-positive (+). When many bacteria bind to a solid surface, it will ○ walking pneumonia Thermoplasma form a thick layer of cells called biofilm. ○ this bacteria have a rough membrane Another function of other surface layers are virulence factors (molecules that contribute to the pathogenicity of a bacterial pathogen) and preventing dehydration. 2.5 LPS: THE OUTER MEMBRANE ADDITIONAL INFORMATION: In gram-negative bacteria, only a small amount of the Biofilm total cell wall consists of peptidoglycan, as most of the Extracellular polysaccharides play a key role in the wall is composed of the outer membrane. development and maintenance of biofilm. The outer membrane is often called the lipopolysaccharide layers, or simply LPS. Example of Microorganisms with thick Capsules with It consists of core polysaccharide, O-specific both containing a thick capsule polysaccharide, Core polysaccharides and Lipid A Bacillus anthracis (lipid portion of the LPS, endotoxin) ○ one causative agent of diseases anthrax The relationship of the LPS layer to the overall ○ capsule is containing protein gram-negative cell wall. Streptococcus pneumoniae It acts as an effective permeable barrier or defense ○ causative agent of bacterial pneumoniae protection against many substances such as lipophilic ○ capsule contains polysaccharide antibiotics (antigen). Encapsulated cells of these bacteria avoid destruction by The outer membrane stabilizes the outer membrane the host’s immune system because the immune cells would structure. recognize these pathogens as foreign and destroy them are blocked from doing so by the bacterial capsule. Periplasm It is the space located between the cytoplasmic and FIMBRIAE, PILI, AND HAMI outer membranes. Fimbriae and pili are thin (2-10 nm in diameter) filamentous structures made of protein that extend 2.7 CELL SURFACE STRUCTURES from the surface of the cell and can have many functions. Fimbriae enables cells to stick to surfaces, including animal tissues in the case of pathogenic bacteria, or MB441 - 1MICRO1 | MENDOZA & ZOLETA 10 University of Santo Tomas - College of Science  to form pellicles (thin sheets of cells on a liquid It is microcompartments and is made of protein or surface) or biofilm on solid surfaces. lipids. Common body inclusions in prokaryotic organisms are: Pili ○ poly-B-hydroxybutyric acid (PHB), a lipid They are similar to fimbriae, but typically longer and that is formed from B-hydroxybutyric acid only one or few pili are present on the surface of the units. cell. The monomers of PHB polymerize All gram-negative bacteria produce pili, and many by ester linkage and then the gram-positive bacteria also contain these structures. polymer aggregates into granules, Pili can be receptors for certain types of viruses, which can be seen either by light or electron microscope. which can be easily seen in the electron microscope The generic term when they are coated with virus particles. poly-B-hydroxyalkanoate (PHA) is Pili facilitates genetic exchange between cells in a often used to describe this class of process of conjugation (conjugative or sex pili). carbon- and energy-storage Pili enables the adhesion of pathogens to specific polymers. host tissues that they subsequently invade (type IV ○ Glycogen, which is a polymer of glucose; and other pili). like PHA, glycogen is a reservoir of both carbon and energy and is produced when carbon is in excess. ADDITIONAL INFORMATION: ○ Polyphosphate, Sulfur, and Carbonate Minerals Pili (IV Type Pili) Many prokaryotic and eukaryotic All gram-negative bacteria produce pili, and many microbes accumulate inorganic phosphate in the form of gram-positive bacteria also contain these polyphosphate granules as a result structures. when phosphate is limiting, as a Type IV pili not only facilitate adhesion but also source of phosphate for nucleic acid support an unusual form of cell movement called and we call this phospholipid twitching motility in certain bacterial species. biosynthesis. ○ Certain species such as Pseudomonas The oxidation of sulfide generates electrons for use in and Moraxella energy metabolism (chemolithotrophy) or 𝐶𝑂2 fixation Type IV pili can be implied as key colonization (autotrophy) factors for certain human pathogens. Contrary to known filamentous cyanobacteria forming carbonate minerals on the outside, some ○ Examples are gram-negative pathogens cyanobacteria form carbonate minerals inside the Vibrio cholerae (cholera) and Neisseria cell, as cell inclusions. gonorrhoeae (gonorrhea) and the ○ Example of this is the cyanobacteria gram-positive pathogen Streptococcus Gloeomargarita as it forms intracellular pyogenes (strep throat and scarlet fever) granules of benstonite (a carbonate mineral It can also mediate genetic transfer by the process that contains barium, strontium, and of transformation in some bacteria, which along magnesium. Biomineralization is the microbiological process of with conjugation and transduction, are the three forming minerals. known means of horizontal gene transfer. Some bacteria can orient themselves within a magnetic field because they contain magnetosomes. ○ Magnetosomes impart a magnetic dipole on 2.8 CELL INCLUSION a cell, allowing it to orient itself in a magnetic field. ○ It is commonly found in aquatic organisms Inclusion functions as energy reserves and/or carbon that grow best at low oxygen levels or reservoirs or have special functions. anaerobic conditions. Thus, hypothesize that Storing carbon or other substances in an insoluble the magnetosomes help the organisms be form is advantageous because it reduces osmosis guided downward toward the sediments stress that the cell would encounter should the same where oxygen is low or present. amount be dissolved in the cytoplasm. Example of this organism is the Magnetospirillum magnetotacticum MB441 - 1MICRO1 | MENDOZA & ZOLETA 11 University of Santo Tomas - College of Science  Magnetotaxis is the process of migrating along Earth’s magnetic field lines. 2.10 ENDOSPORES ADDITIONAL INFORMATION: Bacterial Endospore is formed during endosporulation or sporulation. Sulfur Bacteria It functions as survival structures and enables the Many gram-negative Bacteria and Archaea oxidize organism to endure unfavorable growth conditions. reduced sulfur compounds, such as hydrogen Bacterial endospores are extremely resistant to sulfide; this is what we call “sulfur bacteria.” heat, harsh chemical, radiation, desiccation (drying), and nutrient depletion. First discovered by Sergi Winogradsky There are layers that are absent in vegetative state endospores: ○ Calcium (DPA) is complexed with dipicolinic acid which accumulates in the core. 2.9 GAS VESICLES ○ Small, acid-soluble spore protein (SASP), which functions to bind DNA and protect it from damages Gas Vacuoles or Vesicles’ main function is to ○ Dehydrated core provide buoyancy of bacteria and allow cells to ○ Spore coat, composed of layers of position themselves in regions of the water column spore-specific proteins that best suits their metabolism. ○ The outermost layer, exosporium (a thin ○ This is not found in microbial eukaryotes. protein covering) It can be easily dispersed by wind, water, or through animal gut, thus endospores are highly distributed in ADDITIONAL INFORMATION: nature. Blooms ENDOSPORE FORMATION AND GERMINATION Typically found in lakes, these are gas-vesiculate microbes that are cyanobacteria that are formed in There are three steps in the formation and massive accumulation. germination of an endospore: activation, They rise to the surface of the water and are blown germination, and outgrowth. by the wind. ○ Cells do not sporulate when they are actively growing but only when growth ceases owing GAS VESICLES STRUCTURE to the exhaustion of an essential nutrient. Activation occurs when endospores are heated for It is conical-shaped in structure and made of two several minutes at an elevated but sublethal distinct proteins: temprated. ○ The major gas vesicle protein, GvpA, forms ○ Activated endospores are then conditioned to the watertight vesicle shell and is a small germinate when supplied with certain hydrophobic, and very rigid protein. nutrients, such as certain amino acids. ○ Multiple copies of GvpA align to form the Germination is a rapid process (occuring in a matter parallel “ribs” of the vesicle. of minutes) signaled by the loss of refractility of the The minor protein, GvpC, functions to strengthen the endospore and loss of resistance to heat and shell of the gas vesicle by cross-linking and binding chemicals. the ribs at an angle to group several GvpA molecules Outgrowth involves visible swelling due to water together. uptake and synthesis of RNA, proteins, and DNA. They can vary in size depending on the different ○ The vegetative cell emerges from the broken species from about 300 to more than 1000 nm and in endospore and begins to grow. It remains in width from 45 to 125 nm. the state until the environment signals once They are impermeable to water and solutes but again to trigger sporulation. permeable to gases. MB441 - 1MICRO1 | MENDOZA & ZOLETA 12 University of Santo Tomas - College of Science  THE SPORULATION CYCLE 2.11 FLAGELLA, ARCHAELLA, AND SWIMMING MOTILITY Sporulation is a form of cellular differentiation and many genetically directed changes in the cell occur 2.11 FLAGELLA, ARCHAELLA, AND SWIMMING during the conversion from vegetative growth to MOTILITY sporulation. Many Bacteria are motile by swimming due to a Endosporulation requires differential protein structure called the flagellum while the present synthesis. structure in Archaea is called the archaellum. ○ This occurs by the sequential activation of Another function of the flagella is to attach itself (or several families of endospore-specific genes microbe) to the surface and for virulence factors. and the turning off of many vegetative cell Bacterial flagella are long, thin appendages (15-20 nm functions. wide, depending on the species) free at one end and anchored into the cell at the other end. A group of flagella is known as a tuff. ○ The arrangement of flagella can be either polar-one space or tuff-in groups. Flagella do not rate at a constant speed but increase or decrease their rotational speed in relation to the strength of the proton motive force/ ○ The rotation resembles a propeller. It can go up to 1100 revolutions per second. ○ Counterclockwise movement is the flagella moving forward ○ Clockwise movement is the flagella moving to stop and stumble. PATTERNS OF FLAGELLA PATTERN EXPLANATION Monotrichous There is one flagella at the end. ADDITIONAL INFORMATION: Peritrichous Flagella is found all over the cell; tuff is found. Sporulation of some Bacteria The Bacillus subtilis’ conversion of a vegetative Lophotrichous Flagella is only found at the end of cell into an endospore takes about 8 hours and the cell; typically a tuff begins with asymmetrical cell division. The proteins encoded by sporulation-specific Amphitrichous Flagella is found on both sides of the genes catalyze the series of events leading from cell the moist, metabolizing, vegetative cell to the relatively dry, metabolically inert, but extremely FLAGELLA STRUCTURE AND ACTIVITY resistant endospore. Flagella are not straight but are helical. The flagella consists of the following parts: IV. CELL LOCOMOTION ○ Filament is composed of many copies of protein called flagellin. There are two major types of prokaryotic cell ○ Hook is a wider region at the base of the movement: the swimming and gliding motion. filament and it consists of a single type of protein and connects the filament to the flagellum motor in the base. MB441 - 1MICRO1 | MENDOZA & ZOLETA 13 University of Santo Tomas - College of Science  ○ Basal body consists of the flagellum motor which are the rotor and the stator. Hydrotaxis It is the movement toward water receptors for hydration. 2.12 GLIDING MOTILITY Osmotaxis Movement toward or away pressure or high ionic strength. Bacteria who are lacking a flagella are still motile cells by relying on the gliding motility. Scotophobotaxis A bacteria avoids entering darkened It is a smooth, continuous motion and is done by spots or habitats when they are moving. helical intracellular protein track. OTHER MOTIONS OF GLIDING MOTILITY UNIT EXTRA INFORMATIONS MOTILITY EXPLANATION The largest Bacteria known to man is Thiomargarita namibiensis while the smallest is Mycoplasma Twitching Motility This motility requires a pili and pneumoniae. its common motion is by Mycoplasma is considered pleomorphic. extending, attaching, and retracting. It uses energy from ATP hydrolysis. Surface Motility A movement usually done when moving away from the colony. 2.13 CHEMOTAXIS AND OTHER TAXIS The ability of a cell to move toward or away from various stimuli has ecological significance in that the directed movement may enhance a cell’s access to resources or allow it to avoid harmful substances that could damage or kill it. ○ It is a result of evolution as a means to respond to the gradients of different factors. CHEMOTAXIS AND OTHER TAXIS TAXIS EXPLANATION Chemotaxis The cell moves towards a chemical (either run or tumble) reactant gradient. It tries to either move to a higher concentration or away from the concentration. Phototaxis Phototrophic microorganisms move towards light enabling them to position themselves to efficiently receive light for photosynthesis. Aerotaxis Movement toward or away from oxygen. MB441 - 1MICRO1 | MENDOZA & ZOLETA 14 University of Santo Tomas - College of Science