422 



Illinois Natural History Survey Bulletin 



Vol. 23, Art. 4 



method of rennet production (Society of 

 American Bacteriologists, Committee on 

 Bacteriological Technic, 1939), whey and 

 hard curd are produced in 20 minutes by 

 isolate 4, in 18 hours by isolate 2 and in 

 40 hours by isolates 1, 3 and 5. In shake 

 cultures, each isolate grows throughout 

 the agar. The least amount of growth 

 develops in the upper quarter inch of 

 medium. On agar in Petri dishes, each 

 isolate grows beneath and beyond both 

 microscope slides and Petri dish bottoms 

 placed on the surface of the medium. 



The optimum temperature for growth 

 of the organism is approximately 24 to 

 30 degrees C, maximum about 37 degrees 

 C. and minimum 5 degrees C. or lower. 

 Potato dextrose agar slant and shake cul- 

 tures held at —12 degrees C. for 4 days, 

 then incubated at 24 degrees C, produce 

 abundant growth within 3 days, with 

 conspicuous gas production in the shake 

 cultures. The thermal death points for 

 the five isolates are 15 minutes at 55 

 degrees C, for isolates 1, 3 and 5; 10 

 minutes at 55 degrees C. for isolate 2 

 and 10 minutes at 45 degrees C. for isolate 

 4. The optimum pH range for growth 

 is 6.82—7.50, the maximum is pH 10.00-|- 

 and the minimum is pH 4.67. 



Biochemical Reaction. — Growth of 

 the organism in gelatin stabs is beaded 

 and most abundant at or near the surface 

 but absent beyond 15 mm. below the sur- 

 face. There is no liquefaction and the 

 medium is unchanged. Colonies on gelatin 

 are punctiform, convex, entire, smooth 

 and translucent. Nitrates are reduced to 

 nitrites without the formation of gas. 

 Indole is not formed. Hydrogen sulfide 

 is produced. Asparagin stimulates growth 

 without the production of gas in synthetic 

 peptone-free medium (Society of American 

 Bacteriologists, Committee on Bacteriolog- 

 ical Technic, 1939). The medium be- 

 comes alkaline. Starch is not hydrolyzed. 

 Both the methyl red and Voges-Proskauer 

 tests are positive. Pectin is not fermented 

 by the method described by Elrod (1942). 



All fermentation tests to determine the 

 sources of carbon that these five isolates 

 utilize were run in duplicate and in 

 parallel series on nutrient broth and syn- 

 thetic peptone-free basic media. Both 

 types of basic media were used, since 

 Burkholder (1932) has pointed out that 

 accurate results in carbohydrate fermen- 



tation tests frequently are not obtained 

 when strong alkali-producing bacteria are 

 grown in beef-extract-peptone broth. One 

 per cent of each carbon was used except 

 for trehalose, melibiose and cellobiose, 

 where 0.5 per cent was used. These 

 isolates produced both acid and gas from 

 arabinose, rhamnose, xylose, dextrose, 

 fructose, galactose, mannose, lactose, malt- 

 ose, trehalose, melibiose, cellobiose, manni- 

 tol, sorbitol and salicin. They produced 

 slight acid and gas from starch, slight acid 

 but no gas from glycerol in nutrient broth, 

 alkali and no gas from glycerol in synthetic 

 peptone-free medium, and no acid or gas 

 from inulin, dextrin or filter paper. Acid 

 and gas were not produced by these isolates 

 from elm sawdust in nutrient broth or 

 from elm sawdust in synthetic peptone-free 

 medium when the medium was autoclaved 

 after the sawdust was added. However, 

 there was slight acid and no gas produc- 

 tion in the synthetic peptone-free medium 

 when the elm sawdust was autoclaved 

 before it was added to the sterile medium. 

 Variable results were obtained with su- 

 crose, raffinose, melezitose and dulcitol. 

 Isolates 1, 3 and 5 produced alkaline re- 

 action, without the formation of gas, from 

 all four carbons. Isolate 2 produced acid 

 and gas from sucrose and raffinose and an 

 alkaline reaction without gas from melez- 

 itose and dulcitol. Isolate 4 produced 

 both acid and gas from all four carbons. 

 Variation in ability of these five isolates to 

 ferment sucrose, raffinose, melezitose and 

 dulcitol is not believed to be sufficiently 

 significant to separate them as distinct 

 species. 



Taxonomy 



The organism constantly associated with 

 wetwood of elm in Illinois is similar in 

 many respects to Erwinia salicis Day. 

 However, it reacts differently from E. 

 salicis by producing gas from most of the 

 sources of carbon that were tested. In 

 addition, it changes litmus milk, produces 

 hydrogen sulfide and does not produce a 

 bright yellow pigment on potato. Also, it 

 is similar in many respects to Pseudomonas 

 lignicola Westerdijk & Buisman (1929), 

 which inhabits the wood of elms in Hol- 

 land. However, it differs from P. lignicola 

 as follows. It produces gas from dextrose- 

 and most other sources of carbon tested,! 





