The relationship between critical pressure and width of gas vesicles in isolates of Planktothrix rubescens from Lake Zürich

Abstract

The mean critical collapse pressure (p c ) of gas vesicles in 81 strains of the cyanobacterium Planktothrix rubescens from Lake Zu $ rich, Switzerland, was bimodally distributed between a minimum of 086 MPa and a maximum of 117 MPa. Measurements were made of the cylinder diameter (d) of gas vesicles isolated from seven of the strains. The mean diameter, which varied from 48 to 61 nm, was inversely related to p c , in keeping with the theory of strength of thin-walled rigid cylinders. These measurements extended the range of p c -width relationship of gas vesicles, which can be described by the expression p c l 461(d/nm) N1n53 MPa. p c was correlated with gas vesicle genotype (see the accompanying paper by S. J. Beard, B. A. Handley, P. K. Hayes & A. E. Walsby, Microbiology 145, 2757-2768) : of the 81 strains investigated, all those with the gas vesicle genotype GV2 produced gas vesicles with a mean p c of less than 10 MPa, whereas those of GV3 had a mean p c of greater than 10 MPa. It is suggested that gas vesicles of the GV3 strains, which are narrower and stronger than any previously recorded in freshwater cyanobacteria, have evolved to withstand the high hydrostatic pressures during deep winter mixing in Lake Zu $ rich.

The diversity of gas vesicle genes in Planktothrix rubescens from Lake Zürich

“…Strains of a variant that contain a shortened form of gvpC, lacking a 99 nt section, produce gas vesicles that have a higher p c (Bright & Walsby, 1999). We demonstrate that single filaments of these variants can be identified by PCR amplification using gvpA-and gvpC-specific primers.…”

The daily integral of growth by Planktothrix rubescens calculated from growth rate in culture and irradiance in Lake Zürich

“…Gibson & Foy (1983) found no photoinhibition of growth rates under short light periods in Limnothrix (Oscillatoria) redekei. It is inevitable that different strains will have differences in growth rates ; Bright & Walsby (1999) have commented that even the increased costs of making narrower gas vesicles in some strains of Planktothrix in Lake Zu$ rich might result in lower growth rates.…”

Gas vesicles in actinomycetes: old buoys in novel habitats?

“…The function of GvpG, -K and -O is still unclear; however, GvpC provides rigidity to the vesicle but is not essential for vesicle integrity. Moreover, GvpC has been suggested to shape gas vesicles [5][6][7][8].…”