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BACTERIA AND VIRUSES
Bacteria
Bacteria are microscopic single-celled organisms that thrive in diverse environments. They can live within soil, in the ocean and inside the human gut.
Structure of Bacteria
Bacteria composes of cytoplasm, cell wall, ribosomes and flagella.
Classification of bacteria• Classification – ordering
• Nomenclature – naming• Often immortalizes the
person who discovered it or its origin– Escherichia coli Theodor Escherich
– coli from colon
• Distinguishing –identification
Classification of bacteria
• *Kingdom• Phylum• Class• Order• Family• *Genus ( 1st name)• *Species ( 2nd name identifier)
Classification of bacteria
• Morphology – shape, color, gram specificity
• Metabolism
• Molecular techniques – Forensics, DNA finger prints, RNA, protein analysis
Species Transmission Diseases
Bacillus anthracis
Contact with sheep, goats and horsesInhalation or skin penetration through abrasions of spore-contaminated dust
Cutaneous anthraxPulmonary anthraxGastrointestinal anthrax
Bordetella pertussis
Contact with respiratory droplets expelled by infected human hosts.
Whooping coughComplications:Secondary bacterial pneumonia
Clostridium tetaniSpores in soil infecting puncture wounds, severe burns or surgery
Tetanus
Corynebacterium diphtheriae
Respiratory dropletsPart of human flora Diphtheria
Escherichia coli (generally)
Part of gut flora, spreading extraintestinally or proliferating in the GI tract
Urinary tract infections (UTI)DiarrheaMeningitis in infants
Enterotoxigenic Escherichia coli (ETEC)
Faecal-oral through food and waterDirect physical contact
Traveller's diarrhea
Bacterial Diseases
Species Transmissions Disease
E. coli O157:H7 Reservoir in cattle Hemorrhagic colitisHemolytic-uremic syndrome
Francisella tularensis
Vector-borne by anthropodsInfected wild or domestic animals, birds or house pets
Tularemia
Haemophilus influenzae
Droplet contactHuman flora of e.g. upper respiratory tract
Bacterial meningitisUpper respiratory tract infectionsPneumonia, bronchitis
Helicobacter pylori
Colonizing stomachUnclear person-to-person transmission
Peptic ulcerRisk factor for gastric carcinoma and gastric B-cell lymphoma
Legionella pneumophila
Droplet contact, from e.g. cooling towers, humidifiers, air conditioners and water distribution systems
Legionnaire's DiseasePontiac fever
Leptospira interrogans
Food and water contaminated by e.g. urine from wild or domestic animals. Leptospira survives for weeks in stagnant water.
Leptospirosis
Species Transmission Disease
Mycobacterium leprae
Prolonged human-human contact, e.g. through exudates from skin lesions to abrasion of other person
Leprosy (Hansen's disease)
Mycobacterium tuberculosis Droplet contact Tuberculosis
Mycoplasma pneumoniae
Human floraDroplet contact Mycoplasma pneumonia
Neisseria gonorrhoeae
Sexually transmittedvertical in birth
GonorrheaOphthalmia neonatorumSeptic arthritis
Rickettsia rickettsii
Bite of infected wood or dog tick Rocky mountain spotted fever
Salmonella typhiHuman-humanFaecal-oral through food or water
Typhoid fever type salmonellosis (dysentery, colitis)
Shigella sonneiFaecal-oralFliesContaminated food or water
Bacillary dysentery/Shigellosis
Virus
Classification of virus
Classification of viruses
Viruses were divided into six groups based on the their nucleic acid and m-RNA production.
• 1- ds-DNA viruses.• 2- ss-DNA viruses.• 3- ds- RNA viruses.• 4- ss-RNA viruses with positive strands( positive polarity).• 5- ss-RNA viruses with negative strands(negative polarity).
• 6- ss-RNA viruses associated with the enzyme reverse transcriptase.
Structure of virus• All viruses contain nucleic acid, either DNA or RNA (but not both), and a protein coat, which encases the nucleic acid. Some viruses are also enclosed by an envelope of fat and protein molecules. In its infective form, outside the cell, a virus particle is called a virion.
Viral Diseases
Useful Microbes
Harmful microbes
Harmful microbes
• Bacteria cause lots of different types of disease, from sore throats and food poisoning to swelling of the brain and death of nerves in your skin!
• Some mushrooms can make you sick, even though they look safe to eat. There are fungi that love to make horrible itchy, scaly patches on your skin. Other fungi love the warm, damp skin between your toes and make your skin crack and bleed! If fungi get inside your body, they can cause serious problems.
Harmful microbes
• Viruses cause lots of different diseases, from cold sores and warts to measles, colds and flu! They can be very contagious - they spread very quickly from one person to another. They can even spread in the air, in droplets that form when people cough or sneeze or from surfaces like door handles and telephones! There are very few medicines for viruses, antibiotics don’t work on viruses.
Microbes in human welfare• Microbes in Household products: A common example is the production of curd from milk. Micro-organisms such as Lactobacillus and others commonly called Lactic Acid Bacteria (LAB) grow in milk and convert it to curd. During growth, the LAB produces acids that coagulate and partially digest the milk proteins. It also improves its nutritional quality by increasing vitamin B12. In our stomach too, the LAB play very beneficial role in checking disease causing microbes.
• The dough, which is used for making bread, is fermented by using baker’s yeast (Saccharomyces cerevisiae).
Microbes in human welfare
• “Toddy”, a traditional drink of some parts of southern India is made by fermenting sap from palms.
• Microbes are also used to ferment fish, soya bean and bamboo-shoots to make foods. Cheese, is one of the oldest food items in which microbes were used. The large holes in ‘Swiss cheese’ are due to production of a large amount of CO2 by a bacterium named Propionibacterium sharmanii. The ‘Roquefort cheese’ is ripened by growing a specific fungus on them for a particular flavour.
•Microbes in Industrial products: Production on an industrial scale requires growing microbes in very large vessels called Fermentors.
a) Fermented Beverages: The yeast Saccharomyces cerevisiae used for bread making and commonly called brewer’s yeast, is used for fermenting malted cereals and fruit juices to produce ethanol. Wine and beer are produced without distillation whereas whisky, brandy and rum are produced by distillation of the fermented broth.
b) Antibiotics: Antibiotics are chemical substances, which are produced by some microbes and can kill or retard the growth of other disease causing microbes. Pencillin was the first antibiotic to be discovered and it was a chance discovery. Alexander Fleming while working on Staphylococci bacteria, once observed a mould growing in one of his unwashed culture plates around which Staphylococci could not grow. He found out that it was due to a chemical produced by the mould and he named it Pencillin after the mould Pencillium notatum. Later, Ernest Chain and Howard Florey made its full potential effective antibiotic.
• Enzymes:Lipase – used in laundry detergents
• Pectinase and protease – used in bottled juices• Streptokinase (Streptococcus bacterium) – used as clot buster (to remove clots)
•Bioactive molecules: Cyclosporin A (Trichoderma polysporum fungi) – used as immunosuppressive agent (for organ transplant patients).
• Statins (Monascus purpureus yeast) – used as blood cholesterol lowering agents.
Role of bacteria and viruses in sewage treatment
• Microbes in Sewage Treatment: Treatment of waste waster is done by heterotrophic microbes naturally present in the sewage. This treatment is carried out in two stages;Primary treatment / Physical treatment: It involves physical removal of particles from the sewage through filtration and sedimentation.Sequential filtration – to remove floating debris
• Sedimentation – to remove grit (soil and small pebbles)• All solids that settle form the primary sludge, and the
supernatant forms the effluent. The effluent from the primary settling tank is taken for secondary treatment.
Role of bacteria and viruses in sewage treatment
• Secondary treatment / Biological treatment: The primary effluent is passed into large aeration tanks, this allows vigorous growth of aerobic microbes into flocs. While growing, these microbes consume the major part of the organic matter in the effluent. This significantly reduces the BOD (biochemical oxygen demand) of the effluent. BOD is a measure of the organic matter present in the water. The greater the BOD of waste water, more is its polluting potential.
• Once the BOD of sewage water is reduced significantly, the effluent is then passed into a settling tank where the bacterial ‘flocs’ are allowed to sediment. This sediment is called Activated sludge.
Role of bacteria and viruses in sewage treatment
• A small part of this sludge is pumped back into the aeration tank to serve as the inoculum.
• The remaining major part of the sludge is pumped into large tanks called anaerobic sludge digesters.
• During this digestion, bacteria produce a mixture of gases such as methane, hydrogen sulphide and carbon dioxide. These gases form biogas.
• The effluent from the secondary treatment plant is generally released into natural water bodies like rivers and streams.
Images of bacteria
Images of virus
-Kushwanth.P