Imaging mass spectrometry of intraspecies metabolic exchange revealed the cannibalistic factors of Bacillus subtilis.
During bacterial cannibalism, a differentiated subpopulation harvests nutrients from their genetically identical siblings to allow continued growth in nutrient-limited conditions. Hypothesis-driven imaging mass spectrometry (IMS) was used to identify metabolites active in a Bacillus subtilis cannibalism system in which sporulating cells lyse nonsporulating siblings. Two candidate molecules with sequences matching the products of skfA and sdpC, genes for the proposed cannibalistic factors sporulation killing factor (SKF) and sporulation delaying protein (SDP), respectively, were identified and the structures of the final products elucidated. SKF is a cyclic 26-amino acid (aa) peptide that is posttranslationally modified with one disulfide and one cysteine thioether bridged to the α-position of a methionine, a posttranslational modification not previously described in biology. SDP is a 42-residue peptide with one disulfide bridge. In spot test assays on solid medium, overproduced SKF and SDP enact a cannibalistic killing effect with SDP having higher potency. However, only purified SDP affected B. subtilis cells in liquid media in fluorescence microscopy and growth assays. Specifically, SDP treatment delayed growth in a concentration-dependent manner, caused increases in cell permeability, and ultimately caused cell lysis accompanied by the production of membrane tubules and spheres. Similarly, SDP but not SKF was able to inhibit the growth of the pathogens Staphylococcus aureus and Staphylococcus epidermidis with comparable IC(50) to vancomycin. This investigation, with the identification of SKF and SDP structures, highlights the strength of IMS in investigations of metabolic exchange of microbial colonies and also demonstrates IMS as a promising approach to discover novel biologically active molecules.
Liu
Wei-Ting
WT
Department of Chemistry and Biochemistry, University of California at San Diego, La Jolla, CA 92093, USA.
Yang
Yu-Liang
YL
Xu
Yuquan
Y
Lamsa
Anne
A
Haste
Nina M
NM
Yang
Jane Y
JY
Ng
Julio
J
Gonzalez
David
D
Ellermeier
Craig D
CD
Straight
Paul D
PD
Pevzner
Pavel A
PA
Pogliano
Joe
J
Nizet
Victor
V
Pogliano
Kit
K
Dorrestein
Pieter C
PC
D001412:Bacillus subtilis / Q000737:chemistry* / Q000378:metabolism; D001426:Bacterial Proteins / Q000032:analysis*; D013058:Mass Spectrometry / Q000379:methods*; D015394:Molecular Structure; D013171:Spores, Bacterial
D001426:Bacterial Proteins
Mol Microbiol. 2009 Nov;74(3):609-18
19775247
Science. 2003 Jul 25;301(5632):510-3
12817086
Trends Microbiol. 2008 Jun;16(6):269-75
18467096
Nature. 1997 Nov 20;390(6657):249-56
9384377
Cell. 2006 Feb 10;124(3):549-59
16469701
Nat Chem Biol. 2009 Dec;5(12):885-7
19915536
PLoS Genet. 2006 Oct;2(10):e135
17069462
Curr Opin Microbiol. 2009 Apr;12(2):205-14
19251475
Cell. 1991 Feb 8;64(3):545-52
1846779
Mol Microbiol. 2003 Dec;50(5):1683-701
14651647
FEBS Lett. 2007 Jan 9;581(1):151-6
17184776
J Appl Microbiol. 2001 Dec;91(6):1044-50
11851812
Nat Rev Microbiol. 2007 Mar;5(3):219-29
17277796
Nat Methods. 2007 Oct;4(10):828-33
17901873
Proc Natl Acad Sci U S A. 2000 Jul 5;97(14):8063-8
10869437
Proc Natl Acad Sci U S A. 2008 Nov 25;105(47):18126-31
18776051
Science. 2009 Jul 10;325(5937):161-5
19589993
J Bacteriol. 2008 Nov;190(21):6983-95
18723616
J Bacteriol. 2006 Apr;188(7):2692-700
16547057
Curr Opin Microbiol. 2007 Dec;10(6):638-43
17977783