Bacterial Growth Curve – منحنى نمو البكتيريا

Bacterial Growth Curve – منحنى نمو البكتيريا


Today, we will discuss the
Bacterial Growth Curve. First of all, we should keep
in mind that bacteria multiply by binary fission. So if we
have a bacteria like this the cell wall will do like this,
and the cell will be divided into two This is called binary fission; the single cell gives rise
to two, the two become 4, 4 become 8, 8 become 16,
16 become 32, 32 become 64 and so on Again this is the binary fission When we grow a bacterial culture,
where do we grow it? We grow it in an artificial
medium to feed on Bacteria grow on humans because they
find a suitable medium for their growth We grow bacteria in an
artificial medium to cultivate them and to
diagnose the type of bacteria We take a bacterial sample from
the patient, if he is infected with pneumonia, we will take
the sample from the sputum if infected with meningitis,
we take the bacteria from the CSF (cerebrospinal fluid)
then we grow this bacteria Bacteria usually grow after 24 hrs,
others grow in two to three weeks like TB Some bacteria grow quickly like E. Coli So, they vary in their growth periods.
Alright. Scientists examined what happens
during those 24 hrs of growth. Let’s draw a curve On the y-axis is the number of bacteria, on the x-axis is the time per hrs Will the bacterial curve start from zero?!
No, this means there is no bacteria actually We definitely have some bacteria here This amount of bacteria is called: Inoculum This is the amount of
bacteria placed to start a culture, it needs to
be small in amount. This bacterial curve shows four lines Each line has a name. The first line is called: Lag Phase The second is called: Logarithmic Phase.
This is Lag and the other is Log. This is the Stationary Phase This is the Decline Phase So bacteria undergo four
phases during growth By the way, these phases are like engagement
and marriage, what do I mean by this? The lag phase is the engagement
period, they are still introducing themselves to one another. The organism
is adapting itself to the culture media OK? The bacteria is constant, it
doesn’t increase or decrease in number. It can decrease
but it doesn’t increase In the lag phase, the number
of bacteria is constant But the size increases the activity also increases So everything increases
except the number of bacteria as the bacteria is still adapting
itself to the new environment In the log phase, the couple is now married
and they have many children; two, four, 8, 16, they are looking for them in the logarithms
table, they don’t even know their names This is the logarithmic phase. It shows severe increase in number the size decreases This is the bacterial cell, it undergoes
binary fission, so it gets smaller, and the activity increases. So now the couple have so many
children, they need to control birth now So that was engagement,
marriage and giving birth then birth control. This is
called the stationary phase. The number of newly formed
bacteria=number of death so the number of bacteria remains constant Now, pay close attention
to what I am going to say The number of living bacteria
is called the viable count The number of dead and living
bacteria is called: Total Count. Now, let’s see how the curve will be like. In this phase, some bacteria
are being formed, others are dying So the total count increases (the
number of newly formed and dead cells) but the viable count is constant Understood? The viable count doesn’t
change because the number of dead cells is equal
to the newly formed ones But when we look up the total population
of Egyptians from the year 1930, for example, we will get the number
of dead and alive people altogether Let’s move on to the decline phase. The bacteria has now increased so
much in number, so the nutrition decreases, the oxygen requirement
decreases and the pH changes So the bacteria start dying, and
continue to die until the medium reaches complete sterility; meaning
it becomes clear of bacteria Now, do you understand the
bacterial growth curve? Alright The bacteria was grown on a media plate, artificial one, but what happens if
this bacteria enters the human body? The same thing happens, with
change of the phases names Instead of the lag phase, we
call this: Incubation Period. This is the time taken by the bacteria to
show its symptoms after attacking the body For example, if I got
infected with measles, once the symptoms appear, I
will calculate the period taken by the bacteria
after it attacked my body to this moment of symptoms appearance.
This is the incubation period This is the invasive period, where
the bacteria is increasing in number or signs and symptoms period. This is when the patient starts complaining
about his body temperature, body pain, vomiting or diarrhea, when the bacteria,
in its large numbers, is invading his body When we start taking antibiotics,
and bear in mind that there is a difference between
antibodies and antibiotics antibodies are an immune response and antibiotics are the drugs and others. After administering antibiotics,
some bacteria die and others live That is the course of the disease. For example, I fell sick during
the period from 17/4 to 19/4, and the immune system won over the bacteria as the antibiotics killed the bacteria,
so they die and then we call this period Convalescent phase The symptoms disappear gradually
during this phase until the patient is completely cured when the bacteria
reach sterility (zero in number) Understood? This is a piece of cake 🙂 How can I count bacteria? This is so
important in medicine and dentistry Why? We need to know how many bacteria
live in a root canal, for example. We need to know the number of
bacteria in blood; Bacteremia. So we have viable count and total count. The total count is calculated
using hemocytometer. We place a sample in the
hemocytometer and then count the RBCs, WBCs and platelets
then multiply by a factor. Alright. The bacteria shows turbidity
when grown on a fluid medium. So what can we do about this? We prepare different turbid bacterial samples then measure the turbidity of
our bacterial sample, and calculate the total
number of bacteria in this sample As for the viable number, We grow it over media we take a certain known
amount of inoculum and grow it over media,
colonies will appear Each coloy is originally
a single bacterial cell count the number of colonies to get
the number of bacteria in medium. If the number of colonies
was so large, we should dilute the bacterial
inoculum or culture. I will keep diluting until I get like 100
colonies, this is still a large number by the way, but I will continue to multiply
by the dilution factor and total amount I get the viable number of bacteria,
the living bacteria only. Alright? The living bacterial cells are counted
with the turbidity meter as well. I observe the turbidity of the bacteria
that results from the increase in number of cells, so we can
roughly estimate the viable count. But the total count is calculated
using the hemocytometer This is how we measure the number
of bacteria, either viable or total. Total count means both living
and dead. Viable is only living

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11 thoughts on “Bacterial Growth Curve – منحنى نمو البكتيريا”

  • انا امتحنت خلاص النهاردة 😄 وكنت عايزة اشكر حضرتك علي كل معلومة فهمتها من حضرتك باسلوب سهل ومبسط جدا 😇 ربنا يكرم حضرتك ويجازيك خير ان شاء الله

  • جزاك الله خيرا عن كل حرف بتعلمه لينا , بجد لما بسمع حضرتك بفتخر اني خريج الازهر , ربنا يزيدك فهما و علما

  • دكتورهہ • says:

    طبعا اني عراقية وبحثت على Bacterial Growth وطلعت انت دكتور شرحك حلو جدا و لطيف ، فهمت المادة عليك تسلم دكتور و الله يحفظك 💕🌸

  • Nermeen George says:

    الله ينور عليك يا دكتور انا بكتب كل محاضرات حضرتك وابيضها بتساعدنى جدااااا …شكرااا لحضرتك متابعة من الدوحة- قطر

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