Bacterial loss and degradation of bacterial membrane in preserved seawater samples

The present study reports the loss of bacteria in four samples preserved with formaldehyde and stored at 4°C in the dark. The degradation of bacterial membrane was estimated by BacLight probe and related to storage time, bacterial loss and attachment to the bottle surface. The concentration of bacteria decreased sharply in the first week of storage in two out of the four samples. After 3 months of storage, the final concentrations of bacteria were between 30 and 63% of the initial concentration in three out of the four samples. A linear decrease in the ratio of intact bacteria of 6–8% over a 10 day period was observed. The attachment of bacteria onto the bottle surface did not seem to play an important role in bacterial loss. The results of this study suggested that bacteria in seawater samples should be enumerated as soon as possible after sampling, in order to minimise error.