1 2 . Xanthomonas 



The genus Xanthomonas is quite well defined. Typical species 

 are characterized by their polar monotrichous flagellation, the 

 yellow water-insoluble pigmentation, and rather feeble oxidative 

 metabolism of glucose and some other carbohydrates. Nonflagel- 

 lated strains are common. The phytopathogenic types are best 

 known, but nonpathogenic types also exist. 



Cultures 



Thirty-nine cultures were studied of which thirty-eight were 

 phytopathogenic types received from Dr. M. P. Starr of the Uni- 

 versity of California. Of these thirty-eight cultures twenty-one 

 were typical with polar monotrichous flagellation. The rest were 

 either nonflagellated (seventeen strains) or atypical in other re- 

 spects. Only one nonpathogenic culture was studied, namely, 

 Xanthomonas arsenooxydans, received from the National Collec- 

 tion of Industrial Bacteria (NCIB) as 8688. 



Fig. 14. a. Xanthomonas campestris, XC-16. Polar monotrichous flagella. 



b. X. campestris, XC-16. This picture is included to show the very rare 

 occurrence in Xanthomonas of two flagella at the same pole. 



c. X. amaranthicola, XA-12()R. Polar monotrichous flagella. 



d. X. amaranthicola, XA-120R. This picture may be interpreted in two 

 ways, either as representing one organism with two different polar flagella, or 

 as two organisms, each with a different polar flagellum. The wavelength of the 

 shorter flagellum is exactly one half that of the longer flagellum. 



e. X. papavericola, XP-161. Polar monotrichous flagella. 



f. X. manihotis, XM-12. Rather long polar flagellimi but otherwise typical. 



g. X.vignicola, XV-118. Long polar flagellum with irregular wavelengths 

 and amplitudes. This was common in some strains. 



h. X.ricinicola,XR-lOl. Typical polar flagellum. 



i. X. rubrilineans, XR-2. Polar monotrichous flagellation. 



j. X. zinniae, XZ-101. Typical polar flagellum. 



k. X. zinniae, XZ-101. This illustrates a variant with a flagellum of longer 

 than average wavelength. 



1. X.tardicrescens, ST-1. The average wavelength of this species is signifi- 

 cantly shorter than that of the more typical Xanthomonas species. 



m. X. arsenooxijdnns, NCIB 8688. Polar monotrichous flagella. Note the 

 rather long wavelength and coiling tendency of the flagella. 



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