HARMFUL EFFECT OF BACTERIA
• Cause disease in animals and plants and spoil food.
• Some are saprophytic bacteria cause decay food and make it
unpalatable.
• Few bacteria produce toxic such as potamins in the food.
• Potamins cause food poisoning.
• Ex: Bacterium Clostridium botulinum cause fatal form of food
poisoning known as Botulism.
Bacterial diseases in Man
BACTERIAL DISEASE IN PLANT
Name of disease Cause Signs and symptoms Treatment and prevention
Bacterial leaf spot Bacteria pseudomonas and Necrosis, sometimes leaf spots Eradication of pathogen by
xanthomonas will grow together creating using pathogen tested seeds
large black blotches on leaves and propagated materials
or turning leaves completely and proper spray
black. Shoots, buds flower can
also become black
Blights in plants by bacteria Erwinia amylovora,and Severe yellowing, browning Chemical control less
xanthomonas oryzae spoting, withering, or dying of effective then biological
leaves, flowers, fruits, control methods.
parenchyma cells damage
Bacterial soft roots Bacterium Erwinia Plant tissue becomes Proper inspection of plant
carotovora macerated seeds, control weeds, avoid
harvesting under wet
conditions, Avoid bruising
Bacterial wilt disease in Bacterium Erwinia Wilt diseases caused by Control of bacterial wilt
plants tracheiphila blocking of the vessels of host depends on control of its
plants by masses bacteria as a insects beetle vectors. Use of
result plant wilt and dies insecticides
Control of harmful bacteria
Bacterial harmful activities can be controlled by certain chemicals
referred as disinfectants, antiseptics, antibiotics, and
antimicrobialchemicals
1. Sterilization is the process of destroying all living organisms
and viruses
2. Disinfection is the elimination of microorganisms, but not
necessarily endospores, from inanimate objects or surfaces.
• An ideal disinfectant or antiseptic (chemical agent) kills
microorganisms in the shortest possible time without damaging
the material treated.
There are different chemical that are used as disinfectant some are as follows:
a) Phenol: One of the first chemicals to be used for disinfection was phenol. It is
standard for most other antiseptics and disinfectants. (Disinfectants are used
to kill germs on nonliving surfaces. Antiseptics kill microorganisms
on your skin.
d) Soaps and detergents: Soaps and detergents decrease the surfacetension
between microorganisms and surfaces, and thereby help cleanse the surface.
e) Aldehydes: Two aldehydes, formaldehyde and glutaraldehyde,inactivate
microbial proteins by crosslinking the functional groups in the protien
f) Ethylene oxide: Sterilization can be achieved with a chemical known as
ethylene oxide (ETO). This chemical denatures proteins and destroys all
microorganisms, including bacterial spores.
• Halogens: Among the halogen antiseptics and disinfectants are
chlorine and iodine is antiseptic is a tincture of iodine which consists
of halogen iodine. Iodine acts as a bactericidal, fungicide, sporicidal,
etc.
• Heavy metals: A number of heavy metals have antimicrobial ability.
For example, silver is used as silver nitrate in the eyes of newborns to
guard against infection by Neisseria gonorrhea.
g) Oxidizing agents: Oxidizing agents such as hydrogen peroxide kill microorganisms by
releasing large amounts of oxygen, which contributes to the alteration of microbial
enzymes
h) Food preservatives: Foods can be preserved by using a number of organic acids
to maintain a low microbial population. Benzoic acid, Ascorbic acid etc.
3. The use of Antibiotics
Antibiotics are compounds that are mostly derived from
biosynthesis of other microorganisms. Streptomyces and
Penicillium are two organisms which have given us antibiotics.
Antibiotics act in different ways to kill microorganisms like:
• Antibiotics that inhibit cell wall synthesis
• Antibiotics that inhibit protein synthesis
• Antibiotics that Inhibit Nucleic Acid Synthesis or DNA
Replication
• Antibiotics that Interfere with Metabolic Pathways
Physical method to control harmful bacteria
Boiling: 100 °C denatures proteins
and
. alters membranes and destroy
bacteria ex. Cooking,
Incineration: Exposure to
flame or destroy bacteria by
burning.
Refrigeration: Temperature 0 °C to 7 °C,
Inhibits metabolism, Preservation of
food or laboratory materials.
Refrigeration preserves food by slowing
down the growth and reproduction of
microorganisms as well as the action of
enzymes which cause food to rot.
Freezing food slows down
decomposition by turning residual
moisture into ice, inhibiting the growth
of most bacterial species
High-pressure processing:
Exposure to pressures of
100-800 MPa, denatures
proteins and can cause cell
lysis, Preservation of food.
Freezing: Below -2 °C, stops
metabolism, may kill
microbes, Long-termstorage
of food, laboratory cultures,
or medical specimens.
Hyperbaric oxygen therapy:
Inhalation of pure oxygen at a
pressure of 1-3atm, Inhibits
metabolism and growth of
anaerobic microbes,
Treatment of certain infections
(e.g., gas gangrene)
OR
Administration of 100%
oxygen to greater than 1 atm
i.e where oxygen dissolve in
arterial blood plasma in
increased amount thus this
dissolved plasma oxygen is
carried to different tissue.
Autoclave: Heating at very high
temperature like 121 °C for 15-40 minutest
15 psi, denature proteins and alters
membranes.
Pasteurization: 72 °C for 15 seconds 138 °C for 2 seconds (UHT),Denatures proteins and
alters membranes it prevents spoilage of milk, apple juice, honey, and other ingestible
liquids.
• In food industry the processing steps required to eliminate the potential for foodborne
illness is known as preservation process.
• Pasteurization: Is one of the traditional preservation process, and use thermal energy
to increase the product temperature and inactivate specific pathogenic
microorganisms.
Lyophilization: Rapid freezing under vacuum, inhibits
metabolism and preserve food this method is used in
laboratory cultures, or reagents.
Or In which water is removed from a product after it is
frozen and placed under a vacuum allowing the ice
change directly from solid to vapor without passing
through a liquid phase.
Membrane filtration:
• Use of membrane filter
with 0.2-um or smaller pore
size, physically removes
microbes from liquid
solutions.
• It is used in removal of
bacteria from heat-sensitive
solutions like vitamins,
antibiotics, and media with
heat-sensitive components
Simple desiccation: Drying, Inhibits metabolism, Dried fruits, jerky.
Reduce water activity: Addition of salt or water, inhibit metabolism
and can cause lysis.
RADIATIONS
