Abstract
The form studied was obtained by Mr. W. Meehan from the intestines of a Cerambycid beetle. It proved to be a true purple bacterium with the characteristics of Molisch's Rhodobacillus palustris. 1
The Molisch group of the purple bacteria was omitted in a previous study by one of us. Here the spectra of various purple bacteria were considered, including the sulphur bacteria, brine bacteria and the lichen symbiont Chiodecton. 2 It seemed, therefore, desirable to determine the spectrum characteristics of the Rhodobacillus.
Microspectra were taken with the microspectrograph 3 on Wratten panchromatic film of a very thin layer of pure culture bacteria (one bacillus thick). A control photograph of the lamp was taken on the same film.
The negatives were measured out by means of densitometer attachment to the radiomicrometer. 4 First the raw data were used to calculate the position of the absorption bands. It was found that Rhodobacillus is a true purple, inasmuch as the position of the bands agrees closely with the data already obtained (Becking 1. c.). The extrapletions were carried out by means of a triple set of assumed wave lengths and the prismatic spectrum converted by means of v. Hartmann's formula.
By the use of Schwartzschild's law the per cent absorption for various wave lengths was determined by means of comparison with the lamp negative. The following table shows the absorption for various wave lengths:
The absorption characteristics of a somewhat thicker layer of Rhodobacillus was ascertained by means of a radiomicrometer and glass screens. The light-green “Corning” screen transmitted only visible light between 680 and 400 μm . The other screen was a carbon glass which transmitted only infra red up to the visible red.
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