Question

8. Why did you use an inoculating loop instead of a needle to make the transfers from the culture plates to the culture tubes? 9. How do the pure broth cultures differ? The slant cultures? 10. What is the function of sterile mineral oil in the maintenance of stock cultures? 11. Describe how a culture can be lyophilized. 12. How can some anaerobes be maintained in pure cultures? 13. What are some signs of growth in a liquid medium? 14. In summary, what is the major purpose of this exercise? Culture Transfer Instruments, Techniques, and Isolation and Maintenance of Pure Cultures 93

Answer 1

8.An inoculation loop is usually used because it speards easily over a greater volume without affecting or damaging the gel. in case of needle which could pierce the gel , because it has a pointy end . On the other hand it is generally used for stabbing the bacteria( stab culture) . 9.Pure culture is a liquid media whereas slant culture is a semi solid media .    10. The sterile oil maintain the various aspects in the agar medium . it maintain the moisture of the agar enviroment . it provide dissolved oxygen and maintaining the culture for longer periods .It lowers the orgamism's metabolism thus saving energy. 11. Lyophilization is a process where watery subtances removed from a frozen product via a process called sublimation , in which a frozen liquid passes directly into a gasseous state without entering a liquid phase .
Stock cultures to be lyophilized were grownfor 18 to 24 h on solid media appropriate to their
nutritional requirements.The entire bacterial cell mass was removed from the surface of the agar and placed in the suspending medium by means of a sterile cotton swab. The bacterial
suspension was mixed vigorously to obtain a homogeneous suspension and placed into a sterile
VacVial containing 10 of the capillary tubes.Filling of the capillary tubes then occurred spontaneously
by capillary action. The VacVial was stoppered, placed in a -70°C alcohol bath, and
allowed to freeze. The contents of the vials were dried for 16 to 18 h under a vacuum of 30 gm of
Hg .After lyophilization, the vials were sealed withtheir rubber stoppers and stored at -20°C.    12. For maintaining anaerobes in the pure culture must be avoid of oxygen . which become detrimentous for their growth . They are usually inoculated in a agar slant using an inoculated needle. They grow properly in the anarobic enviroment. 13. Cloudiness of the liquid is one of the improtant sign . Various bacteria grown in liquid cultures often form colloidal suspensions.