5 1 . Caulobacter 



In Bergey's Manual is listed only one species of Caulobacter, 

 Caulobacter vibrioides. This organism is one of the most common 

 bacteria in natural waters. It is present in the distilled water of 

 the author's laboratory at all times. When bacterial cultures are 

 washed for flagella staining a few caulobacter may invariably be 

 found on the slides and may be mistaken for a variant of the cul- 



FiG. 57. a. Caulobacter vibrioides. A typical in(li\'idiuil organism showing 

 a single polar flagellum of very short wavelength. 



b. C. vibrioides. This pictnre shows an individual with a stalk and a flagel- 

 hun at the end of the stalk. 



c, d, e. C. vibrioides. Here are shown various degrees of rosette formation. 

 The individuals appear to be attached to each other. Flagella develop on the 

 daughter cells when division is about complete. 



f. C. vitjrioides attached by a stalk to a staphylococcus. The Caulobacter 

 Hagellum is still attached to the end of the stalk. 



g, h. C. vibrioides attached to an unidentified water organism with a single 

 polar flagellum. Note the difference in wavelength of the flagella of the un- 

 identified organism and Caulobacter. 



i. C vibrioides attached to Salmonella wichita. There are several salmon- 

 ella in the clump and the flagella with the longer wavelength are salmonella 

 flagella. The smaller organisms around the periphery are Caulobacter and 

 two of these at the bottom of the picture show flagella. 



j. C vibrioides attached to Sareina ttreae. The rounded curves of several 

 sarcinae may be seen along the upper right edge of the dense mass. Several 

 sarcinae flagella of long wavelength emerge from the upper part of the clump 

 and one from the lower part. Many caulobacter flagella are evident. 



k. C. vibrioides. The three pictures show the morphology of caulobacter 

 in slightly alkaline media of pH 7.5 to 8.0; pH 8.0 was the upper limit for 

 growth. In the somewhat alkaline medium caulobacter grew very poorly and 

 produced few stalks and few flagella. Note the strongly curved soma. The 

 organism shown in the upper right was very exceptional in having both a stalk 

 and a flagellum. 



1. C. vibrioides. In media with osmotic pressure equivalent to about 1% 

 sodium chloride and at a pH not lower than 6.5, caulobacter grows slowly and 

 in the form of long and somewhat curved filaments. The filament may have a 

 single polar flagellum as illustrated, one or more lateral flagella or, most fre- 

 quently, no flagella. 



m. C. vibrioides from a mixed culture with Bacillus pumilis. This is a 

 rather unusual involution form. 



n. C. vibrioides rosette from which has grown out a long filament. This 

 picture is from a normal culture in which filaments are extremely rare. Note 

 the flagellum at the end of the filament. 



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