ZoBell — 40 — Marine Microbiology 



in order to cool them to 20° or 25° C. because many marine microorganisms 

 are injured by being exposed to higher temperatures for a few minutes. 

 Before the agar has congealed, the prescription bottle is placed on its side. 

 In most cases the agar congeals in a smooth layer which permits colonies 

 to be counted. With an inoculating needle having one end bent at right 

 angles, colonies can be transferred to other media for further study. 



Counts obtained on prescription bottles under controlled conditions 

 in the laboratory compare favorably with Petri dish counts. For work at 

 sea the prescription bottles have the advantage of being economical and 

 easy to pack. With them it is not necessary to transfer the media as it is 

 when pouring Petri dishes. This saves time and minimizes the possibili- 

 ties of contamination. The screw-top caps prevent the dehydration of 

 the media. Prescription bottles have been used by the author for plating 

 bacteria in a row boat as well as on sea-going research vessels. Their use 

 for plating water bacteria was first observed by the author in the labo- 

 ratory of Dr. Elizabeth McCoy at the University of Wisconsin. Henrici 

 and McCoy (1938) used prescription bottles for plating bacteria from 

 lakes. 



The six-ounce prescription bottles can also be used for 90-ml. and 99-ml. 

 dilution water blanks as well as for enrichment media receptacles. For 

 example, when looking for nitrifying bacteria, it is very simple to intro- 

 duce I-, 10-, and loo-ml. quantities of sea water into prescription bottles 

 containing a suitable ammoniacal saline solution. After they are inocu- 

 lated, they can be compactly stored or incubated in either an upright or 

 horizontal position until ready for examination. 



Further details concerning the use of enrichment media for the detec- 

 tion of various physiological types of bacteria and other analytical proce- 

 dures will be given in the following chapters. 



The rowboat crane for hauling limnological apparatus, described by 

 Brown and Ball (1940), has proved to be very useful for collecting 

 samples from a small boat. 



