Cyanobacterial lipopolysaccharides and human health – a review

Abstract

Cyanobacterial lipopolysaccharide/s (LPS) are frequently cited in the cyanobacteria literature as toxins responsible for a variety of heath effects in humans, from skin rashes to gastrointestinal, respiratory and allergic reactions. The attribution of toxic properties to cyanobacterial LPS dates from the 1970s, when it was thought that lipid A, the toxic moiety of LPS, was structurally and functionally conserved across all Gram-negative bacteria. However, more recent research has shown that this is not the case, and lipid A structures are now known to be very different, expressing properties ranging from LPS agonists, through weak endotoxicity to LPS antagonists. Although cyanobacterial LPS is widely cited as a putative toxin, most of the small number of formal research reports describe cyanobacterial LPS as weakly toxic compared to LPS from the Enterobacteriaceae.We systematically reviewed the literature on cyanobacterial LPS, and also examined the much lager body of literature relating to heterotrophic bacterial LPS and the atypical lipid A structures of some photosynthetic bacteria. While the literature on the biological activity of heterotrophic bacterial LPS is overwhelmingly large and therefore difficult to review for the purposes of exclusion, we were unable to find a convincing body of evidence to suggest that heterotrophic bacterial LPS, in the absence of other virulence factors, is responsible for acute gastrointestinal, dermatological or allergic reactions via natural exposure routes in humans.There is a danger that initial speculation about cyanobacterial LPS may evolve into orthodoxy without basis in research findings. No cyanobacterial lipid A structures have been described and published to date, so a recommendation is made that cyanobacteriologists should not continue to attribute such a diverse range of clinical symptoms to cyanobacterial LPS without research confirmation.

Sensitivity of salad greens (Lactuca sativa L. and Eruca sativa Mill.) exposed to crude extracts of toxic and non-toxic cyanobacteria

“…This compound is considered to be produced by all cyanobacteria and is a structural constituent of the outer layers of the cell wall (Metcalf and Codd, 2004). Cyanobacterial LPS is attributed with a range of pathological effects in humans, from cutaneous signs and symptoms, gastrointestinal illness, respiratory disease, allergy, headache and fever (Stewart et al, 2006). On aquatic community, studies demonstrate that cyanobacterial LPS stimulate drinking in fish, the increased volume of water in the gut potentially increases the opportunity for uptake of toxins (including MC) from the water and promotes osmoregulatory imbalance on rainbow trout (Best et al, 2003).…”

Cyanobacterial Toxins of the Laurentian Great Lakes, their Toxicological Effects, and Numerical Limits in Drinking Water

“…It has been suggested that the LPS of cyanobacteria may cause or contribute to human illness, particularly in causing epidermal allergic reactions. However, there is little evidence in the scientific literature that skin contact with the LPS of cyanobacteria causes a skin rash [53,54]. Rather, it may be that skin rashes after cyanoHAB exposure are caused by one of hundreds of other bioactive metabolites produced by cyanobacteria.…”

Substances bioactives élaborées par des cyanobactéries isolées de certains écosystèmes aquatiques marocains

“…Dans ces milieux aquatiques, les cyanobactéries sont souvent l'origine d'intoxications mortelles de troupeaux d'animaux domestiques ou sauvages, de poissons, d'oiseaux et même de l'Homme. En effet, les cyanobactéries sont capables de produire des substances possédant des propriétés toxiques à savoir l'hépatotoxicité, la neurotoxicité, la dermatotoxicité et les syndromes gastro-intestinaux [2][3][4]. En revanche, plusieurs travaux ont montré que les cyanobactéries constituent une nouvelle source de composés bioactifs [5][6][7].…”