Biochemistry and microbiology of some Irish Sea sediments: II. Bacteriological analyses

The numbers, distribution, some physiologicla properties and, to a small extent, the taxonomy of heterotrophic bacteria from several Irish Sea cores are described. The presence of molds in the cores is also reported. An attempt is made to compare the physiological properties of the organisms, particularly those involving organic nitrogen requirements and extracellular proteolytic enzyme production, with the known biochemical characteristics of the sediments from which they were taken.     

Biochemistry and microbiology of some Irish Sea sediments: I. Amino-acid analyses

Cores of sedimentary mud, collected on a transect between the Isle of Man and Ireland, were qualitatively analysed for free amino acids by thin-layer chromatography of the dansylated (DNS) derivatives. The DNS derivatives of isoleucine/leucine and α-aminobutyric acid were found in all samples, while the derivatives of phenylalanine, valine, arginine and ammonia were usually present. Acid hydrolysis followed by treatment with ninhydrin showed the presence of peptidyl amino acids in half the DNS-reacted extracts. No distribution pattern of amino acids was found either with geographical location or down the depths of the cores. Attempts to quantify the method were unsuccessful. Other analyses indicated the presence of glucose/galactose, but no neutral or phospholipids or recognizable plant pigments were identified.     

Temperature-induced changes in the formation of sulphide in a marine sediment

The influence of temperature upon sulphide formation was investigated with sediment sulphureta incubated at constant temperatures in the laboratory. The concentrations of sulphate, sulphide and pyrite were periodically measured and it was found that, in addition to a decrease in the rate of sulphide formation with temperature, there was a changes in the origin of the sulphide. Thus, at 5° and 10°C, the majority of sulphide originated from organic sulphur, while sulphate contributed the greater proportion of the sulphide at 20° and 30°C. Such changes presumably reflect those in the natural enviroment during winter and summer.     

The effect of microbial activity upon the sedimentary sulphur cycle

The sulphate content of an intertidal sediment at Anglesey (UK) was shown to vary during the year, the sulphate-reducing activity of the microbial population being limited by low temperature during winter, and by the low numbers of sulphate-reducing bacteria during May, 1969. A corresponding annual variation of the sedimentary sulphide could not be demonstrated, and the sulphide which was formed biologically during the course of the year was almost entirely lost from the sediment. This loss of sulphide was probably due to subsurface oxidation; and flushing, by water entering at the base of the sediment. It is suggested that sulphide was only precipitated within the sediment during summer when sulphate reduction was active, and even then only during part of the tidal cycle when flushing did not occur.     

The seasonal selection by temperature of heterotrophic bacteria in an intertidal sediment

The seasonal selection by temperature of bacteria in an intertidal sediment was investigated, and a simplified method of demonstrating the temperature adaption of a mixed heterotrophic bacterial population was suggested. The method relied upon counting the bacteria which grew at only two separate incubation-temperatures, and compared favourably with more tedions methods which utilise replicated cultures grown at a large number of incubation temperatures. Using this technique, a temperature adaptation index was calculated for the heterotrophic bacterial population and changes in the value of this index were shown to be correlated with seasonal changes of environmental temperature.     

Some observations on the interactions of marine protozoa and crude oil residues

Marine protozoa were observed to take up Kuwait crude-oil residues in the laboratory and the field. The results suggest that the ingestion occurs only whilst the organisms are feeding on normal food sources.