# Bacterial activity

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• Bacterial activity

# Gram-positive

Cyclic lipodepsipeptides display clear antagonistic activities against Gram-positive bacteria. Syringopeptin 22A, syringopeptin 25A, corpeptin-(SP), tolaasin, and WLIP-(V) all inhibit growth of Bacillus megaterium at similar concentrations (Emanuele et al., 1998Grgurina et al., 2002Bassarello et al., 2004Rokni-Zadeh et al., 2012) while conflicting activities have been reported for syringomycin E and syringotoxin-(SM) (Lavermicocca et al., 1997Scaloni et al., 2004). However, early reports of the biological activity of syringomycin Ps-CLPs were possibly performed with impure preparations that likely contained syringopeptins. Generally, syringopeptins have a higher activity than syringomycins and syringotoxins-(SM) against Rhodococcus and Micrococcus species (Lavermicocca et al., 1997).

# Gram-negative

The vast majority of Ps-CLPs is reported not to show antagonistic activities against Gram-negative bacteria (Lavermicocca et al., 1997Grgurina et al., 2005Lo Cantore et al., 2006Andolfi et al., 2008Sinnaeve et al., 2009a,bReybroeck et al., 2014). As a result, Pseudomonas CLPs tend to be considered ineffective against Gram-negative bacteria. This is generally attributed to the presence of the outer membrane or peptidoglycan layer which hinders access to the plasma membrane (Nybroe and Sørensen, 2004Raaijmakers et al., 2006). However, things are not as clear-cut since CLPs of the tolaasin group (Lo Cantore et al., 2006) and the recently described xantholysin group (Li et al., 2013Molina-Santiago et al., 2015) are able to inhibit Gram-negative bacteria. Furthermore, WLIP-(V) showed a modest activity against the Gram-negative Erwinia carotovora subsp. carotovora (Lo Cantore et al., 2006). To add to the apparent confusion, conflicting activities have been reported against some Xanthomonas species, whereby WLIP-(V) did (Rokni-Zadeh et al., 2012) or did not (Lo Cantore et al., 2006Andolfi et al., 2008) show activity against this Gram-negative bacterium. This notwithstanding, it is clear that the activity of Ps-CLPs should not be considered as limited to Gram-positive bacteria.