The document discusses pathogenic and non-pathogenic bacteria, explaining how pathogenic bacteria can invade host cells and cause disease, while non-pathogenic bacteria, which are primarily beneficial, can become opportunistic pathogens. It covers concepts like pathogenicity, virulence, and the environmental roles of bacteria, highlighting their evolutionary adaptability and mechanisms of disease. Additionally, it details the importance of non-pathogenic microorganisms in food production, nutrient recycling, and overall ecological balance.

1. MARY MATHA COLLEGE OF ARTS & SCIENCES
Department of Biotechnology
By
Dr.S.HIMALINI

2. The Pathogenic bacteria is a biological agent that
causes disease to the host.
 They are often referred to as Infectious agents, so
they have a capability to invade inside the host cells.
Non- pathogenic bacteria inhabit the gut
environment.
These microbes are referred to as gut flora, they live
outside the body cells.

3. Basic structure of bacteria and their
associated environmental reservoirs.

4. Introduction
Our bodies are host to many microbes, most of which
do not cause disease and many of which are beneficial.
Occasionally, however, microbes do cause infection
and disease.
Pathogens such as Staphlococcus, Vibrio
cholera and Mycobacterium tuberculosis differ from
normal non-pathogenic microbes in that they cause
damage to the host.

5. This damage allows the pathogen to colonize
novel sites, antagonizes the host immune
response, and facilitates spread of the pathogen.
The pathogens inflict damage on their hosts by
secreting toxins that act on host cell membranes
or translocate across the cell membrane and
usurp normal cellular functions.

6.  The pathogenic bacteria growing in tissues may form
heterogeneous communities with bacteria expressing
different protein profiles depending on their micro-
environment.

7.  Pathogen emergence is a dynamic, complex, and
multifactorial phenomenon that involves an interplay
of various genetic adaptations and ecological drivers.
Microorganisms are built to evolve.
Bacteria in particular, such as the agents of cholera and
the plague, possess incredibly sophisticated
mechanisms that render them capable of acquiring
pieces of DNA from the environment or accumulating
mutations that allow them to adapt to new
environments in a way that multicellular organisms
such as humans never could. They are essentially
“evolution machines.”

8. Pathogenicity:
 The ability of micro-organisms to induce disease, which may be assessed by
disease- carriage ratios •
 Virulence: The severity of the disease induced by micro-organisms. In
epidemiological studies virulence may be assessed by mortality or morbidity
rates and the degree of communicability
 Reservoir: The place where the organism maintains its presence, metabolizes,
and replicates •
 Source: The place from which the infectious agent passes to the host. In some
cases the reservoir and the source are the same, but not always •
 Infection: A microbiologically proven clinical diagnosis of inflammation.

9. Carriage: Permanent (minimally 1 week) presence of the
same strain in any concentration in body sites normally not
sterile (oropharynx, external nares, gut, vagina, skin) •
Abnormal carrier state: The abnormal carrier state exists
when the isolated micro-organisms is not a constituent of
normal flora (i.e., enterobacterial or pseudomonal strains)
Colonization: The presence of micro-organisms in an
internal organ that is normally sterile (e.g., lower airways,
bladder). The diagnostic sample yields less than a
predetermined level of cfu/ml of diagnostic sample.

10. Factors that Determine the
Pathogenicity
Host susceptibility Presence of mechanisms to fight with the
infection by the host immune system •
pathogenic mechanisms of bacteria Bacterial infectivity, host
resistance, virulence genes, host- mediated pathogenesis (Gram-
negative bacterial sepsis, tuberculosis, and tuberculoid leprosy)
and intracellular growth •
Specific virulence factors Adherence and colonization factors,
invasion factors, presence of a capsule and other surface
components, endotoxins, exotoxins, and siderophores

11. Humans can only pass genes vertically through
generations, that is, from parents to offspring.
 In contrast, bacteria can pass on genes vertically and also
horizontally, trading chunks of genetic information
among one another in ways that can accelerate evolution.
Through this type of gene transfer, some virulence traits
emerge when a cell acquires genetic material from other
microorganisms or from its surrounding environment.

12.  Pathogenicity islands are large clusters of genes that are confined
to pathogenic strains within a species and typically encode
important genes that are critical for host colonization.
For instance, the pandemic strains of V. cholerae harbor several
major pathogenicity islands; one encodes an essential intestinal
colonization factor called toxin-coregulated pilus.
Bacteriophages are viruses that can infect bacteria and in certain
cases can integrate within the genome and confer new traits to the
host cell.
Bacteriophages are a major vehicle for the acquisition of bacterial
toxins in several pathogens.

13. Non-Pathogenic Microorganisms
They are incapable of causing disease. i.e., harmless to other
organisms •
They mostly live in the environment as saprophytes. Some of
them are autotrophs.
Around 99% of bacteria are nonpathogenic.
 They are useful to man as they are involved in
manufacturing foods such as butter, cheese, alcohol, lactic
acid, Probiotics and fermented products, antibiotic, gradual
decomposition of organic matter (dead animals, plants and
their wastes) on or in the soil. • bio fertilizers etc.

14.  Some non-pathogenic bacteria live on the surface of
animals as normal flora.
They are commensals. • But, these bacteria can
become opportunistic pathogens when they invade
the tissues.
For example, E. coli are non-pathogenic bacteria that
live in the gastrointestinal tract and can trigger an
immune response under certain circumstances.

15. Activities of Non-
Pathogenic Microorganisms
Decay
Putrefaction
Fermentation

16.  Petrification
Petrification is the decomposition of proteins (animal matter) under
anaerobic conditions and of carbohydrates (vegetable derivatives starch
or sugar). These two processes transform organic matter into useful
plant foods.
When dead animals and plants are buried in the ground, the soil micro-
flora and the intestinal micro-flora of dead animal enter into the tissue
of the animal or plant.
Decay
Decay is the term used generally to denote the gradua
decomposition of organic matter (dead animals, plants and thei
wastes) on or in the soil.

17. Because of their lipolytic, proteolytic and saccharolytic activities.
The microbes break fats, proteins and sugars, respectively. The
gases (carbon dioxide, ammonia, hydrogen sulphate etc.) liberated
and water formed enter in the air, soil.
Besides, nitrogen, phosphorus, sulfur, produced from dead animal
body combine with water and become soluble and suitable as food
for plants.
Ultimately, the dead animal disappears. Later, the living animals
and men use the plants as food. In this way, the recycle of the
elements is continued.

18. Thus, the life would be impossible on earth without
microbial activity and the microbes are useful or
essential for animal or human life.
 The coli-bacillus and other species of microbes in the
healthy human intestine produce vitamins (B1, B2, B12,
K) essential for the human body.

19. Acidophilic microbes
Acidophilic microbes are beneficial to the human body as they
interfere with the development of pathogenic bacteria which enter
the intestine along with food or drink.
 It is well known that human beings cannot digest directly the
cellulose of the plants and utilise it for their nutrition; but the
stomach micro-flora of ruminants (cattle, sheep, goats) can only
digest it anaerobically and convert into easily digestible end
products like glucose, amino acids, volatile fatty acids, which are
excreted through milk or incorporated in animal tissue or muscle.

20. ii. Microorganism in Food
Moist-less acidic foods (milk, cooked cereals, custard,
soup) are suitable media for the growth of saprophytic
and pathogenic microorganism at warm room
temperature and thus we consume large number of
saprophytic microorganisms along with the foods
every day with no harmful effects.

21. Fermentation
Under anaerobic conditions, the microorganisms
(bacteria, yeasts, moulds) decompose, by their
saccharolytic activities, the carbohydrates (sugars) into
different kinds of acids, such as lactic acid, alcohol, and
gases like carbon dioxide.
 One of the most familiar type of fermentation is the
production of alcohol by yeast from the sugar of fruit
juices as in wine manufacture.