Microbial ecology and Hierarchy

1. Microbial
ecology
&
Ecological
hierarchy

2.  Ecology is the study of how living things
interact with each other and with their
environment.
 The environment of an organism includes two
types of factors: biotic and abiotic.
 Biotic factors are the living aspects of the
environment. They consist of other organisms,
including members of the same and different
species.
 Abiotic factors are the nonliving aspects of the
environment. They include factors such as
sunlight, soil, temperature, and water.

3.  Microbial ecology is the study of how microorganisms
interact with each other and with their environment. It is
also called as Environmental Microbiology.
 The ecological hierarchy begins at the level of individual
organisms.
 A group of organisms of one species living in the same area
and interacting, whether it's humans, cats, or trees, is called a
population.
 Populations of different animals that interact with one another
make up an ecological community - this is where you see
interactions such as predator-prey, parasitism, and
competition.
 An ecosystem includes the community of different species
along with the abiotic environment they live in, like a desert,
rainforest, lake, or tundra.
 The largest ecological level is the biosphere, which is the
entirety of the planet containing living organisms. The Earth's
biosphere includes almost all the land, oceans, and parts of
the atmosphere.

4.  What is ecological hierarchy?
 Levels of biological of organization:
 The levels of biological organization are a
method of arranging living from simplest to
most complex. It starts at the cellular level,
since cells are the basic building blocks of life,
and goes all the way up to the level of the
whole planet. Each level is made of subunits
from the level below. Cells work together to
form tissues, tissues form organs, organs
become organ systems, and a collection of
organ systems makes up an individual
organism.

5.  Microorganisms in ecosystems can have two complementary
roles:
(1) the synthesis of new organic matter from CO2 and other
inorganic compounds during primary production and
(2) decomposition of accumulated organic matter.
 The general relationship between primary producers that
synthesize organic matter and chemoorganotrophic
decomposers was once thought to be quite simple.
 Larger plants and animals contribute to a common pool of
dissolved organic matter (DOM) that is consumed by a variety
of procaryotic and eucaryotic microbes. These microbes then
return some of this DOM to larger animals in the form of
particulate material—that is to say, protists eat bacteria and
primary consumers eat protists (figure 27.13b,c). In addition,
the metabolism and death of these microbes recycles some
organic matter back to the general pool of DOM. This
complex web of interactions is called the microbial loop.

6.  Ecology is the study of how organisms interact with each and
with their environment.
 The ecological hierarchy begins at the level of individual
organisms.
 A group of organisms of one species living in the same area
and interacting, whether it's humans, cats, or trees, is called a
population.
 Populations of different animals that interact with one another
make up an ecological community - this is where you see
interactions such as predator-prey, parasitism, and
competition.
 An ecosystem includes the community of different species
along with the abiotic environment they live in, like a desert,
rainforest, lake, or tundra.
 The largest ecological level is the biosphere, which is the
entirety of the planet containing living organisms. The Earth's
biosphere includes almost all the land, oceans, and parts of
the atmosphere.

7.  Microorganisms thus carry out many important functions as they
interact in ecosystems, including:
 1. Contributing to the formation of organic matter through
photosynthetic and chemosynthetic processes.
 2. Decomposing organic matter, often with the release of
inorganic compounds (e.g., CO2, NH4, CH4, H2) in
mineralization processes.
 3. Serving as a nutrient-rich food source for other
chemoheterotrophic microorganisms, including protozoa and
animals.
 4. Modifying substrates and nutrients used in symbiotic growth
processes and interactions, thereby contributing to
biogeochemical cycling.
 5. Changing the amounts of materials in soluble and gaseous
forms. This occurs either directly by metabolic processes or
indirectly by modifying the environment (e.g., altering the pH).
 6. Producing inhibitory compounds that decrease microbial
activity or limit the survival and functioning of plants and animals.
 7. Contributing to the functioning of plants and animals through
positive and negative symbiotic interactions.

9.  A population consists of all the individual organisms of the same species that
live and interact in the same area. For example, all of the angelfish living in the
same area of the ocean make up the angelfish population.
 A community refers to all of the populations of different species that live and
interact in the same area. The aquatic community that includes the angelfish
also includes the populations of other species of fish, corals, and many other
organisms.
 An ecosystem includes all the living things in a given area, together with the
nonliving environment. The nonliving environment includes abiotic factors such
as water, minerals, and sunlight.
 A biome is a group of similar ecosystems with the same general type of physical
environment anywhere in the world. Terrestrial biomes are generally delineated
by climate and major types of vegetation. Examples of terrestrial biomes include
tropical rainforests and deserts. Aquatic biomes are generally defined by the
distance from shore and depth of water. Examples of aquatic biomes include the
shallow water near shore (littoral zone) and the deepest water at the bottom of a
body of water (benthic zone).
 The biosphere includes every part of Earth where life exists, including all the
land, water, and air where living things can be found. The biosphere is the
largest ecological category and consists of many different biomes.

10.  Key Terms
 mutualism: Any interaction between two species that
benefits both; typically involves the exchange of
substances or services.
 parasitism: Interaction between two organisms, in
which one organism (the parasite) benefits and the
other (the host) is harmed.
 commensalism: Describes a relationship between two
living organisms where one benefits and the other is
not significantly harmed or helped.

11.  Ecological Associations Among Microorganisms
 Despite an apparent simplicity, bacteria can form
complex associations with other organisms. This
process is known as symbiosis. These symbiotic
associations can be divided into parasitism, mutualism
and commensalism. Due to their small size,
commensal bacteria are ubiquitous and grow on
animals and plants exactly as they would grow on any
other surface. However, their growth can be increased
by warmth and sweat; in humans, large populations of
these organisms are the cause of body odor.

12.  PREDATORS
 Some species of bacteria kill and then consume
other microorganisms; these species are
called predatory bacteria. These include
organisms such as Myxococcus xanthus, which
forms swarms of cells that kill and digest any
bacteria they encounter. Other bacterial predators
either attach to their prey in order to digest them
and absorb nutrients, such as Vampirococcus, or
invade another cell and multiply inside the cytosol,
such as Daptobacter. These predatory bacteria
are thought to have evolved from saprophages
that consumed dead microorganisms through
adaptations that allowed them to entrap and kill
other organisms.

13. MUTUALISTS
 Certain bacteria form close spatial associations that are essential for their
survival. One such mutualistic association, called interspecies hydrogen
transfer, occurs between clusters of anaerobic bacteria that consume organic
acids, such as butyric acid or propionic acid, and produce hydrogen; and
methanogenic Archaea, which consume hydrogen. The bacteria in this
association are unable to consume the organic acids since this reaction
produces hydrogen, which accumulates in the bacteria’s surroundings. Only the
intimate association with the hydrogen-consuming Archaea keeps the hydrogen
concentration low enough to allow the bacteria to grow.
 In soil, microorganisms that reside in the rhizospehere carry out nitrogen
fixation, converting nitrogen gas to nitrogenous compound. This serves to
provide an easily absorbable form of nitrogen for many plants that cannot fix
nitrogen themselves. Many other bacteria are found as symbionts in humans
and other organisms. For example, the presence of over one thousand bacterial
species in the normal human gut flora of the intestines can contribute to gut
immunity. Synthesis vitamins such as folic acid, vitamin K, and biotin convert
sugars to lactic acid (see Lactobacillus), as well as fermenting complex
undigestible carbohydrates. The presence of this gut flora also inhibits the
growth of potentially pathogenic bacteria, and these beneficial bacteria are
consequently sold as probiotic dietary supplements.

14. PATHOGENS
If bacteria form a parasitic association with other organisms, they are
classed as pathogens. Pathogenic bacteria are a major cause of human
death and disease and cause infections such as tetanus, typhoid fever,
diphtheria, syphilis, cholera, foodborne illness, leprosy, and tuberculosis.
A pathogenic cause for a known medical disease may only be discovered
many years after, as was the case with Helicobacter pylori and peptic
ulcer disease. Bacterial diseases are also important in agriculture, with
bacteria causing leaf spot, fire blight, and wilts in plants; as well as
Johne’s disease, mastitis, salmonella, and anthrax in farm animals.
Each species of pathogen has a characteristic spectrum of interactions
with its human hosts.

15.  Some organisms, such as Staphylococcus or Streptococcus, can cause
skin infections, pneumonia, meningitis and even overwhelming sepsis, a
systemic inflammatory response producing shock, massive vasodilation,
and death. Yet these organisms are also part of the normal human flora
and usually exist on the skin or in the nose without causing any disease at
all. Other organisms invariably cause disease in humans, such as
the Rickettsia, which are obligate intracellular parasites able to grow and
reproduce only within the cells of other organisms. One species
of Rickettsia causes typhus, while another causes Rocky Mountain
spotted fever. Chlamydia, another phylum of obligate intracellular
parasites, contains species that can cause pneumonia, or urinary tract
infection and may be involved in coronary heart disease. Finally, some
species such as Pseudomonas aeruginosa, Burkholderia cenocepacia,
and Mycobacterium avium are opportunistic pathogens and cause
disease mainly in people suffering from immunosuppression or cystic
fibrosis.

16.  Prescott Microbiology
 https://bio.libretexts.org/Bookshelves/Microbio
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