Swimming motility mutants of marine Synechococcus affected in production and localization of the S-layer protein SwmA.

The S-layer protein SwmA is required for nonflagellar swimming in marine Synechococcus. An analysis of mutations in seven genes at two loci in the Synechococcus sp. strain WH8102 genome indicates that a multicomponent transporter and glycosyltransferases are required for the production and proper localization of SwmA.

SwmB, a 1.12-megadalton protein that is required for nonflagellar swimming motility in Synechococcus.

SwmB is required for swimming motility in Synechococcus sp. strain WH8102. This highly repetitive 1.12-MDa polypeptide is associated with the cell surface, where it is arranged in a punctate manner. Inactivation of swmB does not affect the localization of SwmA, an S-layer protein also required for swimming.

Transposon mutagenesis in a marine synechococcus strain: isolation of swimming motility mutants.

Certain marine unicellular cyanobacteria of the genus Synechococcus exhibit a unique type of swimming motility characterized by the absence of flagella or any other obvious organelles of motility. While the abundant cell surface-associated 130-kDa glycoprotein SwmA is known to be required for the generation of thrust, identification of other components of the motility apparatus has, until recently, been unsuccessful. Here we report on the development of a transposon mutagenesis system for use with marine Synechococcus sp. strain WH8102, a model organism for which the genome has been sequenced. Utilizing this mutagenesis technique, we have isolated 17 independent mutants impaired in swimming motility. These 17 transposon insertions are located in nine open reading frames, which cluster in three separate regions of the genome. Included within these clusters are several multicomponent transport systems as well as a number of glycosyltransferases.

Inactivation of swmA results in the loss of an outer cell layer in a swimming synechococcus strain.

The mechanism of nonflagellar swimming of marine unicellular cyanobacteria remains poorly understood. SwmA is an abundant cell surface-associated 130-kDa glycoprotein that is required for the generation of thrust in Synechococcus sp. strain WH8102. Ultrastructural comparisons of wild-type cells to a mutant strain in which the gene encoding SwmA has been insertionally inactivated reveal that the mutant lacks a layer external to the outer membrane. Cryofixation and freeze-substitution are required for the preservation of this external layer. Freeze fracturing and etching reveal that this additional layer is an S-layer. How the S-layer might function in motility remains elusive; however, this work describes an ultrastructural component required for this unique type of swimming. In addition, the work presented here describes the envelope structure of a model swimming cyanobacterium.

The genome of a motile marine Synechococcus.

Marine unicellular cyanobacteria are responsible for an estimated 20-40% of chlorophyll biomass and carbon fixation in the oceans. Here we have sequenced and analysed the 2.4-megabase genome of Synechococcus sp. strain WH8102, revealing some of the ways that these organisms have adapted to their largely oligotrophic environment. WH8102 uses organic nitrogen and phosphorus sources and more sodium-dependent transporters than a model freshwater cyanobacterium. Furthermore, it seems to have adopted strategies for conserving limited iron stores by using nickel and cobalt in some enzymes, has reduced its regulatory machinery (consistent with the fact that the open ocean constitutes a far more constant and buffered environment than fresh water), and has evolved a unique type of swimming motility. The genome of WH8102 seems to have been greatly influenced by horizontal gene transfer, partially through phages. The genetic material contributed by horizontal gene transfer includes genes involved in the modification of the cell surface and in swimming motility. On the basis of its genome, WH8102 is more of a generalist than two related marine cyanobacteria.

Pulmonary penetration of alpha 1-proteinase inhibitor administered parenterally to dogs.

To study the penetration of alpha 1-proteinase inhibitor (A1Pl) into the lungs of healthy dogs, 83 mg/kg of active A1Pl was administered intravenously over 30 min followed by a bolus of 131I-A1Pl. Animals were lavaged 2 to 72 h after infusion, sequential gamma camera scans were acquired, and urine was analyzed for the excretion of desmosine. After a distribution phase, infused A1Pl left the bloodstream with a half-life of 103 +/- 24 h. Analysis of plasma antiprotease activity demonstrated preservation of function of the infused A1Pl. Lavage fluid A1Pl concentration and activity were significantly increased 24 h after infusion. Gamma camera scans demonstrated that lung, liver, and spleen acquired 131I-A1Pl similarly; radioactivities per gram of tissue of these organs were similar at autopsy. Excretion of desmosine did not decrease from a baseline of 157 +/- 59 nmol/24 h after A1Pl infusion, indicating no effect of A1Pl infusion on background elastolysis. These data suggest that intravenous administration of A1Pl can raise lung antiproteinase levels within 24 h despite the absence of preferential uptake by the lung of the infused protein.