Group 2 conducted several student lab experiments: 1) They determined the effect of hydrogen ion concentration (pH levels of 3, 5, 7, and 9) on the growth of various microbes, finding that most grew at pH 5-9 but not 3. 2) They distinguished aerobic from anaerobic microbes by their growth in nutrient agar tubes with and without homogenization. 3) They tested the effect of four antibiotic discs on bacterial growth in nutrient agar plates, finding zones of inhibition indicating resistance.

1. GROUP 2:
Angga Fatchulloh A. (105090100111009)
Khairatul Insani F. (105090100111031)
Dharma Asih P. (105090101111009)
Lia Rachmawati (105090107111001)
Winda Rahayu (105090113111001)

2.  The growth of every living creature needs sufficient
nutrients and environmental conditions that support for the
growth process, as well as microbes. There are several
factors that can affect the growth of microbes, such as:
temperature, humidity, osmotic pressure, light, pH, and AW
nutrient. Antibiotic resistance is a bacteria that has a set of
ways to adapt for environments that contain antibiotic.
Resistance mecanism include mutations in bacteria,
inhibition of the enzymatic activity of antibiotics, changes in
proteins that are targets of antibiotics, changes in metabolic
pathways and membrane permeability

3.  Student lab can determine the effect of
hydrogen’s ion concentration on the growth
of microbes
 Student lab can distinguish the nature of
microbes based on their oxygen needed
 Student lab can determine the effect of
chemical compounds on the growth of
microbes

4. Physiological pH
Flacon tube with 5 ml
bacteria culture isolates 24
hours
Inoculated into tubes of
glucose phenol red broth
pH indicator, four tubes
should each contain 1 ml
bacteria culture isolates
pH 3 pH 5 pH 7 pH 9
48 hours of incubation at
room temperature

5. Methods

6. Physiological oxygen
Melt the nutrient agar by
steaming, cool to 45
degrees Celcius
Inoculated 0.1 ml bacteria
culture isolates into tubes
of nutrient agar
homogenization
48 hours of incubation
at room temperature

7. Resistance of antibiotic
Flacon tube with 0.9 ml
bacteria culture isolates 24
hours
Inoculated by spread plate
technique 0.1 ml bacteria
culture isolates into plate of
nutrient agar
Fixing four antibiotic discs
to plate of nutrient agar with
the use Laminar Air Flow
(LAF)
48 hours of incubation
at room temperature

8. Results

9. Pict. 1. Tubes which contain of 5 ml Glucose-phenol red broth with power of
Hydrogen (pH) 3,5,7,9 before inoculation and incubation.

10. 2a. 2b. 2c. 2d.
From the pictures above, we know that all of the tubes are shown positive reaction after
incubation by isolates. Pict: 2a. pH 3 2b. pH 5 2c. pH 7 2d. pH 9
Positive reactions: not only indicated by the color change on Glucose-phenol broth but
also can be the formation of a precipitate in the bottom of tube.

11. Table 1. Result of pH’s Effect on Microbial Test
Colour after Inoculation Colour after Incubation Growth On pH
Microbial
3 5 7 9 3 5 7 9 3 5 7 9
orang
K2C1 Yellow Yellow e Red Yellow yellow Dark orange Dark red - - + +
orang
K2C2 Yellow Yellow e Red Yellow orange Red DarkRed + + + +
slightly turbid
orang slightly slightly turbid yellow, there are
H1K2 Yellow Yellow e Red Yellow turbid yellow red deposits + + + +
orang slightly turbid
H3K3 Yellow Yellow e Red Yellow Yellow red turbid red - - + +
orang slightly orange in orange in
H4K2 Yellow Yellow e Red orange surface surface Orange + + + +
orang
Eschericia coli Yellow Yellow e Red Yellow turbid yellow turbid yellow Jingga - + + +
orang
Bacillus cereus Yellow Yellow e Red Yellow turbid yellow Yellow Light Orange - + + +
orang
Salmonella sp. Yellow Yellow e Red Yellow Yellow Light Orange Light Orange - - + +

12. 3a. 3b.
Pict. 3a.Tubes which contain of 10-15 ml Nutrient agar before inoculation
and 3b. After inoculation (growth of aerob bacteria)

13. Cephazoline (+)
Kanamycin (+)
Chlorampenizol (+)
Erythromycin (+)
Pict.4 positive reaction is indicated by clear zone
formation on the medium.

14.  The growth of bacteria is affected by pH, oxygen
and chemicals
 There are several kinds of microbial based on
their need for oxygen: aerobic, facultative
anaerobes and obligate anaerobes
 The effect of chemical compounds can inhibit the
growth of microbes

15. Thank you