Published on September 8, 2013
• Microorganisms are very small organisms which cannot be seen with the unaided eye. • Bacteria, fungi, protozoa, algae, viruses are examples. • Some are pathogenic “germ” ; refers to a rapidly growing cell. What are Microorganisms?
• Ubiquitous • Only form of life for over half of earths entire history so show them some respect!!!! • Humans have co-evolved with microbes. • In earth’s early history microbes were responsible for creating an oxygen based atmosphere. Impact of Microbes on Earth
Microbes are very, very old12 6 39 Our planet is over 4 billion years old
• Eukaryotic Species – A group of closely related organisms that breed among themselves • Prokaryotic species – A population of cells with similar characteristics – Clone population of cells derived from a single cell – Strain genetically different cells within a clone • Viral Species – Population of viruses with similar characteristics that occupies a particular ecological niche Terminology in Micro Bio
• Prokaryotic cells – No nucleus – No membrane bound organelles – Cell wall – Mode of transportation • Eukaryotic cells – Nucleus – Membrane bound organelles – Usually no cell wall – exception fungi Prokaryotic vs. Eukaryotic
• First contained two kingdoms – Plants and animals • Eventually a third kingdom was added – Protista • Finally Whittaker proposed the fourth kingdom for bacteria and a fifth kingdom for fungi A History of Phylogenetic Trees
Bacteria Algae Protozoa Fungi Virus Groups of Microbes
Bacterial Taxonomy Based on Bergey’s Manual • Bergey’s Manual of Bacteriology – five volume resource covering all known procaryotes – classification based on genetic information – phylogenetic – two domains: Archaea and Bacteria – five major subgroups with 25 different phyla
Taxonomic Hierarchy Domain Kingdom Phylum Class Order Family Genus Species Binomial system of nomenclature Dumb Kings Play Chess On Funny Green Squares
• Bacteriology is the study of bacteria • Mycology is the study of fungi • Parasitology is the study of protozoa and parasitic worms • Recent advances in genomics, the study of an organism’s genes, have provided new tools for classifying microorganisms Modern Studies
Classification of bacteria is ‘murky’
3 common shapes Some unusual shapes also: Classification based upon anatomical features
Typical bacteria measure 2-8 m in length and 0.2-2 m in width. Form associations such as chains, clusters, and tetrads.
Other unusual bacteria Spirochetes Cell wall-less Stalked Filamentous Streptomyces Myxobacteria fruiting bodies Classification based upon anatomical features
Gram Positive v/s Gram Negative Hans Christian Gram -- 1884 -- Crystal violet Gram positive structure -- thick layer of peptidoglycan Gram negative structure -- inner vs outer membranes -- lipopolysaccharides and endotoxins Classification based upon staining
Why study Bacterial Cell Structure? Mechanisms of virulence Drug development Identification Some cell exterior structures cell wall cell membrane (lipid bilayer) capsule flagellum pilli
Cell wall • Made up of peptidoglycan. •Responsible for the rigidity of bacterial cell.
Cell Membrane Structure Inner to cell wall, there is a delicate cytoplasmic membrane which surrounds the cytoplasm. Phospholipid bilayers Membrane proteins Membrane fluidity Membranes of thermophilic archaebacteria
Bacterial Flagella Prokaryotic vs eukaryotic Arrangements monotrichous lopho- amphi- peri- Bacterial Flagella
‘Run and Tumble’ pattern How do flagellated bacteria move?
Fimbriae and Pili Fimbriae adhesion to surfaces Pili (pilus) genetic recombination
Endospores Bacillus species can form spores. It is produced within the cell, one spore is formed within a single bacterial cell. It is resistant to heat, UV light, most chemicals and desiccation. When conditions are favorable, the spore germinates and produces a fresh vegetative cell.
Made of polysaccharides which protects bacteria from phagocytes. Capsule
Ribosome is made up of RNA and protein. It is a factory of protein synthesis. Ribosome
An invagination of cell membrane which helps in cell division. Mesosome
Nucleoid (Genetic material) Unlike virus, bacteria have both DNA and RNA. It contains genetic charateristics. Nucleoid
Nutritional Requirements Microorganisms require about ten elements in large quantities, because they are used to construct carbohydrates, lipids, proteins, and nucleic acids. Several other elements are needed in very small amounts and are parts of enzymes and cofactors.
Microbial Growth Conditions 1. Macronutrients 2. Micronutrients 3. Growth factors 4. Environmental factors: temperature; pH; Oxygen et al.
Microbial Nutrition 1. Macronutrients: required in large amounts, including: carbon, oxygen, hydrogen, nitrogen, sulfur, phosphorus (Components of carbonhydrates, lipids, proteins, and mucleic acids ); potassium, calcium, magnesium and iron (cations and part of enzymes and cofactors). 2. Micronutrients: Microbes require very small amounts of other mineral elements, such as iron, copper, molybdenum, and zinc; these are referred to as trace elements. Most are essential for activity of certain enzymes, usually as cofactors. Contaminants in water, glassware, and regular media components often are adequate for growth.
Growth Factors Amino acids are needed for protein synthesis. Purines and pyrimidines for nucleic acid synthesis. Vitamins are small organic molecules that usually make up all or part enzyme cofactors; And only very small amounts are required for growth. (1)amino acids, (2) purines and pyrimidines, (3) vitamins
Nutrition Based Classification of Bacteria Phototrophs • The organisms which depend on sunlight as a major source of energy are called phototrophs Chemotrophs • Other organisms which use chemicals as a source of energy are called chemotrophs. Heterotrophs • Hetrotrophs may either use sunlight or chemical compouds as energy source
Nutritional Types of Microorganisms • Lithotrophs:- Use reduced inorganic substances as their electron source. • Organotrophs:- Extract electrons from organic compounds.
Autotrophs Photoautotrophs Chemoautotrophs Hetrotrophs Photohetrotrophs Chemohetrotrophs Nutrition Based Classification cont.
Major nutritional type Sources of energy, hydrogen/electrons, and carbon Representative microorganisms Photoautotroph (Photolithotroph) Light energy, inorganic hydrogen/electron(H/e-) donor, CO2 carbon source Algae, Purple and green bacteria, Cyanobacteria Photoheterotroph (Photoorganotroph) Light energy, inorganic H/e- donor, Organic carbon source Purple nonsulfur bacteria, Green sulfur bacteria Chemoautotroph (Chemolithotroph) Chemical energy source (inorganic), Inorganic H/e- donor, CO2 carbon source Sulfur-oxdizing bacteria, Hydrogen bacteria, Nitrifying bacteria Chemoheterotroph (Chenoorganotroph) Chemical energy source (organic), Organic H/e- donor, Organic carbon source Most bacteria, fungi, protozoa Nutritional types of microorganisms
Mixotrophic: many purple nonsulfur bacteria 1. No oxygen: photoorganotrophic heterotrophs 2. Normal oxygen: oxidize organic molecules and function chemotrophically. 3. Low oxygen: photosynthesis and oxidative metabolism
Temperature Based Classification of BacteriaPsychrophiles Love to grow in the range of 0 degree Celsius - 25 degree Celsius Mesophiles Love to grow between 25 degree Celsius - 40 degree Celsius Thermophiles Love to grow in the range of 40 degree Celsius - 85 degree Celsius Some species even grow at 98 degree Celsius as in hot sulfur spring
pH Based Classification of Bacteria Acidophiles Neutrophiles Alkalophiles • Love to grow in the range of pH between 0-6 • Love to grow between 6-8 pH • Love to grow at pH above 8
Environmental conditions for microbial growth Some microbes require Oxygen - Aerobic Some microbes live in Oxygen poor environment - Anaerobic
Obligate aerobes Must grow in the presence of air They can not carry out fermentation Microaerophilic bacterium Grow well in low concentrations of oxygen Killed by higher concentrations of oxygen Facultative anaerobe Perform both fermentation and aerobic respiration Can survive in the presence of oxygen Obligate anaerobes Grow in the absence of molecular oxygen Some of these are killed by oxygen Further Classification based on Environmental conditions
In 24 hours some species of bacteria can go from one cell to 16,777,216 cells. Speed of reproduction
• Can and do change over time. • Bacterial populations adapt to changes in the environment. Microbial populations
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