Microbiology sheet (4)

Made by: Hala Nsour

corrected by: Shatha Khtoum

DATE: 29-9-2016

Pre lecture:

There are two examples of positive relationship between organisms:

1- mutualisms: an obligatory relationship between two organisms each one gets the

benefits

2- commensalisms: one gets the benefit and one doesn’t affected.

The microorganisms can have the two relationships in their lives.

Ex: E. coli bacteria act as mutualisms or as commensalisms, which found in all human large

intestines. Humans provide E. coli with food and a place to live. In return, the E. coli digests

food, produces vitamin K and makes it harder for pathogenic bacteria to establish

themselves in our large intestine. And the E. coli may have a commensalisms relationship

with other bacteria (also in the large intestines).

Sometime the waste product of some bacteria become the substrate to other bacteria.

MICROBIAL GROWTH

Microbial growth: Increase in cell number, not cell size!

Physical Requirements for Growth: Temperature • Minimum growth temperature (is the

lowest temperature at which the species will grow). • Optimum growth temperature (is

the temperature at which the species grows best) • Maximum growth temperature (is

the highest temperature at which growth is possible)

Five groups based on optimum growth temperature

1. Psychrophiles (cold- loving microbes)

2. Psychrotrophs

3. Mesophiles (moderate temperature loving)

4. Thermophiles (heat- loving microbes)

5. Hyperthermophiles

Microbial growth (8:50)

Microbial growth: increase in the cell number not cell size

Factor that affect the growth of bacteria can be physical (temperature ,ph ….etc ) or

chemical

It’s important to know the factor which affect the bacteria and know the suitable

environment of bacteria to growth it , and also we should know the negative condition in

order to kill it or control it.

We can't calculate the bacteria by 1, 2, 3, ….etc , we use the log number

Temperature:

- minimum growth temperature : if the temp less than minimum the bacteria will not

grow, more than minimum it will grow

Ex: minimum temp =10 , temp=9 (will not grow),temp=12(will grow)

- maximum growth temp: if the temp more than maximum the bacteria will not grow

,and it will grow if the temp less

Ex: maximum temp=50 ,temp=60(will not grow),temp= 40(will grow)

- optimum growth temperature :best temperature to bacteria growth

* whenever we moved away from the optimum temp the growth will decrease .

* mesophiles are the most bacteria we deal with ,and it's optimum temp between

35_37 (body temperature) .

Optimum growth temperature groups :

1_ psychrophiles (cold-loving microbes): Archea bacteria which live in extreme

environment ( philes =loving ) (live in deep oceans )

2_ psychrotophs (متحملة)

التي تحب وتفضل psychrophiles رودة في حال حدوث ظروف قاسية ,ليست مثلمتحملة للب psychrotophs

البرودة )نموها أفضل بالجو البارد (

3_ mesophiles : which we concerned with ,temp between 35_37

4_ Thermophiles (heat-loving microbes) : we found it in mineral water like Ma'in

waterfalls (60-70)

5_hyperthermophiles : extreme high temp, we found it in magma around the volcanoes.

* (122) is the highest degree that bacteria could tolerate (it’s more than 100, so we

can’t kill the bacteria in boiling water)

Physical Requirements for Growth: pH and Osmotic Pressure Most bacteria grow best between pH 6.5 and 7.5: Neutrophils Some bacteria are very tolerant of acidity or thrive in it: Acidophiles (preferred pH range 1 to 5) Molds and yeasts grow best between pH 5 and 6 Bacteria that thrive in pH of 9-11 are called Alkalophiles Hypertonic environments (increased salt or sugar) cause plasmolysis

Obligate halophiles vs. facultative halophiles

Most bacteria grow best in ph 6.5 and 7.5 : Neutrophils which cause diseases to people

Acidophiles : pH between 1_5 which found in the Mineral water.

Alkalophiles : pH between 9-11 like archea

We can offer suitable ph to bacteria by buffer system .

We can use the Alkalotrophs bacteria (البكتيريا المتحملة للملوحة) in isolated (separation) of

bacteria from each other Ex: vibrio cholera (ph=11)\ staphylococcus aureus

selective medium : only one type of bacteria can live in it ,this selectivity help in

diagnosis and separated the bacteria

the solutions have three type :

1- isotonic solution : like normal saline , no water inter or out from the cell , so the cell

stay at the same shape and size

2- hypertonic solution : according the osmosis; the water go out the cell , and the cell

shrinkage

3- hypotonic solution : the water inter inside the cell and the cell swelling

we can use the hypertonic in preservation of food

halophiles could be obligate or facultative. The bacteria that lives in the Dead Sea is

obligated halophiles.

What we call the followings

Organisms which thrive in high solute – Osmophiles.

Organisms which tolerate high solute – Osmotolerant.

Organisms which thrive in high salt – Halophiles.

Organisms which tolerate high salt – Halotolerant.

Organisms which thrive in high pressure–Barophiles.

Organisms which tolerate high pressure – Barotolerant

* Barophiles found in the oceans

Chemical Requirements for Growth: (25:00) Chemical factors: substance bacteria use as the nutrient for the metabolic reaction

•Carbon is the structural backbone of living matter; it is needed for all the organic compounds that make up a living cell.

•Half of dry weight of bacterial cell is carbon Heterotrophs use organic carbon sources

Autotrophs use inorganic carbon sources •Nitrogen, Sulfur, Phosphorus –N, S Needed for protein synthesis

–N, P used for NA and ATP synthesis

–S in thiamine and biotin Autotrophs: such as glucose

In addition, Microorganisms need

Trace elements

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 the functions of certain enzymes, usually as cofactors.

Oxygen Requirement Types (27:45)

Super Oxide Dismutase (SOD): superoxide radicals convert to hydrogen peroxide & O2.

Catalase: hydrogen peroxide converts to water & O2.

According to oxygen requirement we classified the microorganisms to five different groups

The pathogenic bacteria : according to temperature it’s mesophiles and according to

oxygen requirement it's mostly facultative anaerobe which mean it live in the found or

absence of oxygen .

Ex of facultative anaerobe bacteria E coli

obligate aerobe (هوائية مجبرة): can't live without oxygen

facultative anaerobe (ال هوائية اختيارية): live in the existence or in the absence of

oxygen .

Aerotolerant anaerobe (ال هوائية متحملة)

Strict anaerobe (ال هوائية مجبرة) : exist of oxygen is toxic to it

Microaerophile : need oxygen less than the concentration of oxygen in atmosphere

about 5% ( oxygen in atmosphere 21%)

# the most important two enzymes make the bacteria tolerate or don’t tolerate the

oxygen are Superoxide Dismutase (SOD) and Catalase .

If we take the obligate aerobe bacteria as example and we prepare it and put it in the

Incubator (حاضنة), this bacteria tolerate the oxygen because it has (SOD) and Catalase

enzymes .

while metabolism the sample produce gases one of it is the hydrogen which react with

oxygen to give (H2O2 ) which poisons the bacteria , but because it has (SOD) which will

remove the toxicity and gets rid of oxygen free radicals.

# the incubator is commonly aerobic

#from where the bacteria faces the OH- \ H ? from gases which come from the

metabolic reaction of bacteria .

Coracidium does not have (SOD) or Catalase .

Aerotolerant anaerobe : tolerate the oxygen because it has (SOD) but in small amount , if the amount increase it's will be toxic to it.

Strict anaerobe : can't tolerate the oxygen

Microaerophile : low concentration of oxygen

We have also type of bacteria that need (CO2) more than its concentration in the atmosphere (CO2 in atmosphere less than 1%)

We called this type of bacteria Capnophiles bacteria.

•Low oxygen, high CO2 conditions resemble those found in –intestinal tract

–respiratory tract and

–other body tissues where pathogens grow •E.g: Campylobacter jejuni •Use candle jar, CO2-generator packets, or CO2 incubators Candle jar Capnophiles: Aerobic Bacteria Requiring High CO2

We cultivate this type of bacteria in candle jar (the mechanism)

We put the candle in the jar which will make it consume oxygen and release the CO2

Ex: campylobacter jejuni: the main cause of diarrhea to the children, it's spiral and like seagull wings (جناح النورس).

Anaerobic jar different from candle jar because the candle jar have some oxygen with the CO2 , but the anaerobic jar completely empty of O2 .

Anaerobic Culture Methods (43:50)

•Use reducing media, containing chemicals (e.g. thioglycollate) that combine with O2

•Are heated shortly before use to drive off O2

•Use anaerobic jar

•Novel method in clinical labs: Add oxyrase to growth media OxyPlate (no need for anaerobic jar) .

The Media two type 1- solid 2- liquid (there is a semisolid media but we don't use it in microbiology but in immunology)

1_ Solid: Agar , we can cultivate it in the plate or pipeline (أنبوب), if it in pipeline we called

it Slant (مائل) to increase the surface area of cultivation .

2_ liquid

the growth of bacteria appears in Agar appear like colony

the growth of bacteria appears in Slant appear like colony

the growth of bacteria appears in Liquid appear like terbedity(عكورة).

but in the terbedity we can't know the type of bacteria, and to know it we cultivate it in the Agar so it's will make colony so I can identify the type of bacteria.

if we use liquid we heating it to remove oxygen, or there is another modern way to remove the oxygen: oxyrase enzyme (is an enzyme system that offers a way to remove dissolved oxygen from liquid, gas or semisolid products)

Biofilms (48:30)

Microbial communities used slime for attachment of bacterium to surface structures or to each others. Bacteria communicate by chemicals via quorum sensing which is a system of stimuli and response correlated to population density. Facilitating the transfer of genetic information's (conjugation). Slime Sheltered the bacteria from harmful factors (such as desiccation, antibiotics, and the body's immune system). Slime producing bacteria is the cause of most nosocomial infections

Biofilms: exopolysaccharide layer (طبقة حيوية)

The bacteria either be free living bacteria or Biofilms bacteria

Biofilms is a bacteria linked with a layer (بكتيريا مرتبطة بطبقة), the bacteria be within the layer so it’s more resistant to killing, have more communication to each other, and the transfer of genetic material faster , and it's prevent any inhibitor to reach it because they are integrated (متحدين) , and that’s why the Biofilms are more pathogenic than free living

# now they use the Biofilms instead of some type of antibiotic.