458 Marine Microbiology 



60 /-'moles of ester/ 100 ml in a twenty-fom- hour test period as 

 compared with a yield of 50 /-moles of ester/ 100 ml from 

 n-octadecane under similar conditions. The hydroperoxide assay 

 of Eise and Giesecke (3) was adapted to measurement of alkyl 

 hydroperoxides and yielded evidence of h\ droperoxides in cells 

 grown at the expense of /7-hexadecane. Cells from six liters of 

 medium were extracted with hot reagent grade toluene and 

 yielded as much as 1 /-mole of hydroperoxide, and while these 

 are relatively low levels of hydroperoxide it seems significant that 

 cells grown on non-hydrocarbon substrates never contained such 

 peroxides. The low intracellular levels of hydroperoxide, more- 

 over, are consonant with the relative toxicity of 1-alkyl hydro- 

 peroxides. 



These data, to be presented in detail elsewhere, support the 

 hydroperoxide hypothesis in bacterial oxidation of normal long 

 chain alkanes. 



DEHYDROGENATION OF ALKANES 



The long held notion that dehydrogenation is a step in 

 biological alkanes oxidation seems based upon incomplete identi- 

 fications of "olefins," the ability of paraffin oxidizing micro- 

 organisms to utilize olefins as well as paraffins for growth and 

 energy, and the obvious relationship of chemical structures be- 

 tween the alkane and alkene [see (9) for complete citations]. 

 Support for the hypothesis has come from recent experiments 

 demonstrating that ri-alkanes function as hydrogen donors for 

 reduction of indicators by cell extracts under anaerobiosis (11, 

 18 ) . Senez and Azoulay ( 10 ) have demonstrated a diphosphopyri- 

 dine nucleotide (DPN) dependent heptane dehydrogenase 

 (which requires the presence of pyocyanine) in extracts of P. 

 aeruginosa cells grown at the expense of i7-heptane. We have 

 extensively tested alkane utilizing species of Candida, Nocardia, 

 Pseudomonas, Mycobacterium, and Micrococcus both in the in- 

 tact state and as extracts for ability to reduce various indicators 

 anaerobically in the presence of n-alkanes from decane tlirough 

 octadecane. Our results have been uniformly negative. 



It is difficult to reconcile the findings of Senez and Azoulay 

 (11) with other findings which seem to favor the hydroperoxida- 



