446 BACTERIAL PHOTOSYNTHESIS 



it can outsmart any investigator. This it has been doing consistently for 

 decades, ever since Esmarch first saw it. Now, its cousins and brothers 

 and uncles and aunts have not been tested so earnestly, but I'm sure that 

 if they are, they will all show the same delinquent tendencies. 



First things first! This is a symposium in honor of Professor 

 van Niel— Kees, that is— and itis very much in the nature of an offering 

 from most of us to him, to show him what we have been doing in the 

 last twenty years since he taught us. For many of us had our experience 

 with him over twenty years ago. If we take his 1944 paper as a point 

 of departure for this seminar, you would pretty much have today a 

 synopsis of what has occurred since that paper was published. You 

 may recall that in this classic paper he finished with a plea for bio- 

 chemists to pay some attention to the Athiorhodaceae because they 

 would certainly prove fruitful for further investigation. I forget the 

 exact wording, but that certainly was the sense of it, and a more 

 prophetic statement is hard to imagine. 



Now to get to what has happened in the last twenty years, viewed 

 through the activities of the last three days. I think the easiest thing 

 to do is to begin with the program itself, to take it in large chunks, and 

 to get a bird's-eye view of what has happened. The first three papers 

 of the first day formed a coherent group— which is remarkable even 

 though it was planned that way! These were concerned mainly with 

 chemical aspects of photsynthesis. The first paper, a beautiful pre- 

 sentation by Dr. Jensen on carotenoid biosynthesis, a subject in which 

 Dr. van Niel was interested early, seemed to me definitive, and I 

 believe there is no point in summarizing it because a very adequate 

 summary has been given in her paper in the form of a diagram. What 

 we do derive is the incentive for some biochemistry, I don't think many 

 of the conversions postulated have been placed on a biochemical basis, 

 as far as enzyme content is concerned. It seems to me Dr. Jensen's 

 findings afford a prolific, fertile field for many future Ph.D.'s and 

 for the biochemists hard up for ideas who have graduate students to 

 nurture, and who have somebody intheir vicinity who knows carotenoid 

 chemistry. Perhaps we can build a library of these carotenoids for 

 use as substrates so we can fish out the enzymes. It is about time this 

 was done, even though the carotenoids apparently enjoy less noble 

 status in the field than some other pigments I might mention. 



Now the presentation on tetrapyrroles by Dr. Lascelles and the 

 following one on heme proteins, which were displaced from each other 

 by two days, had been intended to make a logical, consistent unity, and 

 I think they do inasmuch as the cytochromologists had no results which 

 indicated porphyrin types other than those expected. It does appear 

 that there is very little, if any, unusual porphyrin either in the cyto- 

 chromes, or in the unusual heme proteins that are contained in photo- 

 synthetic bacteria, or in green plants. What is unusual are the proteins, 

 and that is where the problem sits now. The capacity of the heme 



