Functional characteristics of culturable bacterioplankton from marine and estuarine environments

Information on the structure of bacterioplankton communities is continuously increasing, while knowledge of their metabolic capabilities remains limited. In this study, the metabolic capacity of bacterioplankton was investigated, as such information is necessary to fully understand carbon cycling and other biogeochemical processes. The diversity of dominant culturable chemoorganotrophic bacteria from one estuarine and three marine environments was analyzed by random isolation of colony-forming units on solid media, taxonomical identification by partial 16S rRNA gene sequence analysis, and functional characterization of the isolates. A total of 76 16S rRNA gene sequences, representing 19 different genotypes, were obtained from the four sampling localities, including Bacillus, Pseudomonas, Pseudoalteromonas, Vibrio, and Erythrobacter as the most frequently isolated genera. The range of metabolic functions possessed by the cultured bacterial assemblages differed significantly between sites. Similarly, the percentage at each sampling station of bacteria capable of performing a specific function was significantly different for 18 of the 25 investigated metabolic functions. At two localities, the bacterial assemblages were dominated by a single genus (Pseudoalteromonas or Erythrobacter) and appeared to be functionally specialized. More than 95% of the isolates were capable of utilizing dissolved free amino acids and protein as their sole nitrogen sources, and all isolates of the specialized assemblages expressed β-glucosidase. Furthermore, only some of the isolates were able to utilize NH4+, while up to two thirds of the isolates of the two marine sites were able to grow on NO3–. [Int Microbiol 2004; 7(3):219–227

Characterization of soluble forms of NCAM

AbstractNeural cell adhesion molecule (NCAM) has been described as a family of membrane glycoproteins. However, soluble NCAM immunoreactivity has long been recognized. We here show that soluble NCAM is composed of two quantitatively major polypeptides of Mr 180 000 and 115 000 and two minor components of Mr 160 000 and 145 000. Soluble NCAM was immunochemically identical to membrane NCAM, was polysialylated and carried the HNK-1 epitope. It only constituted 0.8% of total NCAM in newborn rat brain. Soluble NCAM appeared in neuronal cell culture medium 15–30 min after the start of synthesis preceding accumulation of membrane-associated NCAM on the cell surface. This indicates that soluble NCAM contains a secreted component

The biosurfactant viscosin transiently stimulates n-hexadecane mineralization by a bacterial consortium

Pseudomonas produces powerful lipopeptide biosurfactants including viscosin, massetolide A, putisolvin, and amphisin, but their ability to stimulate alkane mineralization and their utility for bioremediation have received limited attention. The four Pseudomonas lipopeptides yielded emulsification indices on hexadecane of 20–31 % at 90 mg/l, which is comparable to values for the synthetic surfactant Tween 80. Viscosin was the optimal emulsifier and significantly stimulated n-hexadecane mineralization by diesel-degrading bacterial consortia but exclusively during the first 2 days of batch culture experiments. Growth of the consortia, as determined by OD(600) measurements and quantification of the alkB marker gene for alkane degradation, was arrested after the first day of the experiment. In contrast, the control consortia continued to grow and reached higher OD(600) values and higher alkB copy numbers during the next days. Due to the short-lived stimulation of n-hexadecane mineralization, the stability of viscosin was analyzed, and it was observed that added viscosin was degraded by the bacterial consortium during the first 2 days. Hence, viscosin has a potential as stimulator of alkane degradation, but its utility in bioremediation may be limited by its rapid degradation and growth-inhibiting properties