Flotation characteristics of cyanobacterium Anabaena flos-aquae for gas vesicle production

Biogenic gas nanostructures as ultrasonic molecular reporters

Ultrasound is among the most widely used non-invasive imaging modalities in biomedicine, but plays a surprisingly small role in molecular imaging due to a lack of suitable molecular reporters on the nanoscale. Here, we introduce a new class of reporters for ultrasound based on genetically encoded gas nanostructures from microorganisms, including bacteria and archaea. Gas vesicles are gas-filled protein-shelled compartments with typical widths of 45-250 nm and lengths of 100-600 nm that exclude water and are permeable to gas. We show that gas vesicles produce stable ultrasound contrast that is readily detected in vitro and in vivo, that their genetically encoded physical properties enable multiple modes of imaging, and that contrast enhancement through aggregation permits their use as molecular biosensors.

Assembly-driven community genomics of a hypersaline microbial ecosystem

Microbial populations inhabiting a natural hypersaline lake ecosystem in Lake Tyrrell, Victoria, Australia, have been characterized using deep metagenomic sampling, iterative de novo assembly, and multidimensional phylogenetic binning. Composite genomes representing habitat-specific microbial populations were reconstructed for eleven different archaea and one bacterium, comprising between 0.6 and 14.1% of the planktonic community. Eight of the eleven archaeal genomes were from microbial species without previously cultured representatives. These new genomes provide habitat-specific reference sequences enabling detailed, lineage-specific compartmentalization of predicted functional capabilities and cellular properties associated with both dominant and less abundant community members, including organisms previously known only by their 16S rRNA sequences. Together, these data provide a comprehensive, culture-independent genomic blueprint for ecosystem-wide analysis of protein functions, population structure, and lifestyles of co-existing, co-evolving microbial groups within the same natural habitat. The “assembly-driven” community genomic approach demonstrated in this study advances our ability to push beyond single gene investigations, and promotes genome-scale reconstructions as a tangible goal in the quest to define the metabolic, ecological, and evolutionary dynamics that underpin environmental microbial diversity.

Use of cyanobacterial gas vesicles as oxygen carriers in cell culture

The gas vesicles isolated from the cells of filamentous cyanobacterium Anabaena flos-aquae were treated and sterilized with glutaraldehyde and then evaluated for their effectiveness as gas carriers in cell culture. Anchorage-dependent Vero cells were grown in a packed bed of microcarrier beads under the perfusion of Dulbecco's Modified Eagle's Medium with 1% serum. The culture medium supplemented with 1.8% (v/v) gas vesicles was found to support a 30% higher maximum glucose utilization rate than the same medium without gas vesicles. The gas vesicle suspension was confirmed to have no apparent effects on cell metabolism in T-flask cultures. The study results indicated that the gas vesicles, with high oxygen carrying capacity, can be used to increase the oxygen supply in cell culture systems.

Salt stress induces programmed cell death in prokaryotic organism Anabaena

AIMS

Our main interest is to check if programmed cell death (PCD) can occur in prokaryotic algae and if the morphological and biochemical features of PCD are conserved.

METHODS AND RESULTS

Using TUNEL labelling, fluorescence and light microscopy and DNA gel electrophoresis, we found that cell death with features similar to those in metazoan PCD could be induced in different Anabaena strains after exposure to univalent-cation salts at moderate concentration. These features included specific DNA fragmentation, cytoplasmic vacuolation, and the progressive disorganization, fragmentation and subsequent autolysis of the cell corpse. Further analyses of cell viability and proteinase activity revealed that increased protease activities, decreased DNA content, and loss of plasmalemma integrity were related to the PCD process.

CONCLUSIONS

The results showed that like PCD in eukaryotes, PCD in Anabaena is an active process, and is an adaptation to adverse environments. The features of PCD shared between eukaryotes and Anabaena suggest that PCD mechanisms are conserved during evolution.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results will contribute greatly to our understanding of PCD origin and evolution, and are potentially useful in controlling the deluge of algae in some lakes.

Evaluation of oxygen permeability of gas vesicles from cyanobacterium Anabaena flos-aquae

The enhancement of oxygen permeability in aqueous medium by addition of cyanobacterial gas vesicles (GVs) has been examined. The GVs were isolated from cultures of Anabaena flos-aquae that had been cultivated in photobioreactors and harvested by dark flotation. Prior to the permeability experiments, the collected GVs were treated with glutaraldehyde for improved stability. Measurements of oxygen permeability were made with a polarographic oxygen electrode in suspensions of various GV volume fractions (0-2.1%). The experimental results were compared with the values predicted theoretically (Fricke's equation) assuming different permeability through the GVs (PmGV), ranging from 0 to 8.30 x 10(-4) mol m-1 atm-1 s-1. The former corresponded to impermeable vesicles, the latter to air at 22 degrees C as if there were no vesicle wall. The best-fit value of PmGV was 9.9 x 10(-7) mol m-1 atm-1 s-1, ca. 36-fold higher than that in water. GVs were therefore very permeable to oxygen. However, the value was much lower than that predicted for air, implying the existence of wall resistance.