Biochemical and Functional Effects of Sulfate Restriction in the Marine Sponge, Microciona prolifera

The functional and biochemical consequences of sulfate restriction were studied in chemically dissociated Microciona sponge cells maintained in artificial seawater with or without SO42-. In cells pre-treated to reduce preformed secretions, SO42- deprivation reduced cell motility judged by the lack of aggregates in rotating or stationary cultures in comparison with controls. Microscopic examination showed that cells that customarily demonstrate cytoplasmic processes, such as filopodia and pseudopodia, exhibited marked decreases in these cellular processes when maintained in SO42--deprived artificial seawater. Uptake and incorporation of 35SO42- by disaggregated and pre-treated cells was higher under SO42--free conditions relative to controls; this effect was time dependent, rising to a maximum at 12 h, when a three- to seven-fold difference could be demonstrated. 3H-leucine incorporation indicated that protein synthesis was similar in test and control populations. Comparative high voltage electrophoresis of supernatants containing 35SO4 macromolecules from chemically dissociated cells indicated deficiencies of such 35SO4 macromolecules if the rotated cells that released these secretions had been pre-treated in SO42--free artificial seawater. The results of SO42- restriction suggest that secretion of macromolecules or Microciona aggregation factor (MAF), and aggregation and locomotion of Microciona cells depend upon an adequate extracellular source of SO42-, sulfate transport, and sulfation of macromolecules such as polysaccharides.