Bacteria in the intestinal tract of different species of arthropods

The number of bacteria in the intestine of 12 species of arthropods, belonging to 7 different orders, was determined to obtain information about the significance of intestinal bacteria for the digestion of food. Therefore, a simple and effective method for direct counts of 4', 6-diamidino-2-phenylindole (DAPI) stained bacteria from the gastrointestinal tract of arthropods was developed. The intestinal bacteria could be released from the gut wall by ultrasonic treatment in the presence of sodium tetrapyrophosphate (PPi). The bacterial counts ranged between 0.2 and 3.6 x 10(9) (mi gut)(-1) in the foregut, 0.2 and 28 x 10(9) (ml gut)(-1) in the midgut, and 0.1 and 190 x 10(9) (ml gut)(-1) in the hindgut. The foregut and hindgut of Hylotrupes bajules larvae were devoid of bacteria; the whole intestinal tract of Eurycanta calcarata and Schistocerca gragaria contained only low numbers of bacteria. The population of bacteria in some parts of the intestinal tract of several arthropods were high enough to suggest a potential contribution to digestive processes.