The techniques of flow cytometry, scanning and transmission electron microscopy, and confocal scanning laser microscopy were used to study the physiology of Staphylococcus aureus in the early stages of surface-attached culture, and to make direct comparisons with planktonic bacteria grown under the same conditions. Attached bacteria growing in nutrient-rich batch culture were found to go through the same growth phases as equivalent planktonic cultures, but with an exponential growth rate of about half that of the planktonic bacteria. Viability of attached bacteria was very high (around 100%) throughout the first 24 h of growth. The size and protein content of attached bacteria varied with growth phase, and both measurements were always smaller than in planktonic bacteria at equivalent growth phases. Respiratory activity per bacterium, as measured by flow cytofluorimetry, and corrected for cell volume, peaked very early in attached cultures (before the first cell division) and declined from then on, whereas in planktonic bacteria it peaked in late exponential phase. Attached and planktonic bacteria showed thicker cell walls in stationary phase than in exponential phase. Membrane potentials of planktonic and attached bacteria were similar in stationary phase, but were much lower in exponential-phase attached cells than in the equivalent planktonic cells. It is apparent that a range of significant physiological adaptations occur during the early phases of attached growth.

Beach litter found along the Bristol Channel and the coastline of mid-Wales, UK, together with litter obtained from Turkey, Malta, Spain, Tunisia and U.S.A. tourist beaches, and litter gathered from rural roads in Gloucestershire, England, UK, was analyzed by principal component analysis (PCA). PCA distinguished between riverine, sewage-related debris and shipping/fishing source items, but sourcing beach user litter was more problematic. This was attributed to a difference in litter transport mechanisms. PCA for the Bristol Channel distinguished between riverine and marine sources (inner vs. outer channel) and also a sewage sourced group. PCA indicated a land-based source for marine debris found on Mediterranean and USA beaches together with roadside litter from England. Three ‘litter markers’ introduced into the analyses, were comprised of different source groupings: ‘vessels’ (both fishing and other sea going vessels), ‘beach users’, and sewage-related debris (SRD). The former stood out from the latter two markers with beach user and SRD markers appearing to be indistinguishable. The item numbers in each group were six, five and three respectively and this could account for the findings.