In which phase of bacterial growth, cryptic growth occurs?
Cryptic growth means hidden growth of some of individual cells in a starving bacteria in death phase. The majority of cells do not grow at all in death phase but a few cells are able to multiply because these cells use product of lysis of dying cells.
Which amongst the following is an example of monotrichous bacteria?
Among given options, S. aureus is non motile and hence does not have flagella, E.coli and S. typhi both have peritrichous arrangement of flagella. Only V. cholera has monotrichous arrangement of flagella.
Malachite green is used to stain
Bacterial endospores are stained using schaeffer-fulton procedure with malachite green.
A subunit of virus protein coat is called as
The capsomer is a subunit of the capsid , an outer covering of protein that protects the genetic material of a virus. Capsomers self assemble to form the capsid.
Dipicolinic acid is a component of the bacterial
The core of the endospore plays an important role in resistance from various unfavorable conditions. Dipicolinic acid combined with calcium ions is present in the core & plays a part in resistance.
If a bacterial culture has a doubling time of 50 minutes then what will be the specific growth rate?
As specific growth is equal to ln 2/ Doubling time
Specific growth (µ) = 0.693/50
A bacteria divides after every 45 minutes. If a culture containing 107 cells per ml is grown for 180 minutes, what will be the cell concentration per ml after 180 minutes?
Dividing time is 45 minutes. Total time is 180 minutes
Number of generations after 180 minutes = 180 45 = 4
Now applying the formula
N = N0 x 2n where N = Final number of cells., N0 = Initial number of cells
N = number of generations
Choose the correct statement regarding facultative anaerobes amongst the following
Facultative anaerobes are those that does not require O2 for their growth but grows better in the presence of O2.
Whopping cough is caused by
Helicobacter pylori causes the peptic ulcer
Haemophilus aegyptius causes eye infection
Campylobacter jejuni causes diarrahea
Bordetella pertusis causes whopping cough
Match the given substance with the correct method of its sterilization
Culture media is always autoclaved before using. Serum, being highly heat sensitive is always filtered to remove any microbes. Heat sensitive materials like beer is sterilized by pasteurization. Hormones are cold-sterilized using gamma-radiation.
The anti bacterial drug chloramphenicol acts on
Chloramphenicol binds to 23S rRNA of large ribosomal subunit (50S) to inhibit peptide chain elongation during protein synthesis.
Bird flu is caused by
Bird flu is caused by the influenza virus subtype H5N1.
Choose the correct statement (s) regarding acid dyes
Acidic dyes have negative charge and bind to positively charged cell structures. Its examples includes eosin, rore bengal & acid fuschin.
Plasmids are functionally involved in which of the following?
The tra genes present in the plasmid are responsible for the formation of sex pili & the transfer of chromosomal genes from F+/Hfr/F’ cells to F- cells. The transfer of a copy of resistance plasmid results in the transfer of drug resistance genes as well. Transduction is mediated by virus and their is no role of plasmid in transduction.
Which of the following events does not occur during the stationary phase of bacterial growth ?
In stationary phase the cell size does not increase, it remains same and peptidoglycan cross linking also remains the same in stationary phase as the growth rate of cells nearly equal their death rate.
The properties of an episome includes.
An episome is that type of plasmid that can exist both, as an independent entity as well as after integrating into the host’s chromosome. They contain tra operon, where genes are responsible for the formation of the sex pili & the transfer of gene. Plasmids are necessary for conjugation (which is a type of horizontal gene transfer)
Which of the following statements is/are correct for cyanobacteria ?
Cyanobacteria, a group of photosynthetic bacteria can grow easily in a medium exposed to light and air. They perform oxygenic photosynthesis. Some of them are nitrogen fixing in anaerobic conditions but can grow in aerobic conditions.
A culture of bacteria multiply 10 times in two hours. The generation time (in minutes) is______.
A bacterium belonging to cocci group has a diameter of 1 μm. The numerical value of ratio of its surface area to volume is _______
Cocci is sphere shaped structure bacteria
For sphere surface area to volume ratio is 3/a
a = radius of sphere
As per ques, diameter given as 1 µm so radius is 0.5
Therefore surface area to volume ratio is 3/a= 3/0.5 = 6
An experiment is started with 10 number of bacterial cells. After nth generation, the number of cells become 105 cells. The value of n is _________
5 mL of a culture was added to 45 mL of distilled water. This suspension was further diluted to two serial, 1/100 dilutions. 0.1 mL of this final mixture was plated onto an agar plate. Suppose, an average of 137 colonies appeared on the plate after incubation. The CFU/mL of the original sample is _______ ×108.
Total dilutions = 5mL sample in 45 mL diluent = 1/10 = 10-1
It is next diluted by1/100 factor. Hence. 10-3.
Further dilution of 1/100 leads to 10-5.
Hence, Dilution factor = 10-5
Volume plated = 0.1 mL
No. of colonies = 137
CFU = ?