Photorhabdus adhesion modification protein (Pam) binds extracellular polysaccharide and alters bacterial attachment.
BACKGROUND
Photorhabdus are Gram-negative nematode-symbiotic and insect-pathogenic bacteria. The species Photorhabdus asymbiotica is able to infect humans as well as insects. We investigated the secreted proteome of a clinical isolate of P. asymbiotica at different temperatures in order to identify proteins relevant to the infection of the two different hosts.


RESULTS
A comparison of the proteins secreted by a clinical isolate of P. asymbiotica at simulated insect (28 degrees C) and human (37 degrees C) temperatures led to the identification of a small and highly abundant protein, designated Pam, that is only secreted at the lower temperature. The pam gene is present in all Photorhabdus strains tested and shows a high level of conservation across the whole genus, suggesting it is both ancestral to the genus and probably important to the biology of the bacterium. The Pam protein shows limited sequence similarity to the 13.6 kDa component of a binary toxin of Bacillus thuringiensis. Nevertheless, injection or feeding of heterologously produced Pam showed no insecticidal activity to either Galleria mellonella or Manduca sexta larvae. In bacterial colonies, Pam is associated with an extracellular polysaccharide (EPS)-like matrix, and modifies the ability of wild-type cells to attach to an artificial surface. Interestingly, Surface Plasmon Resonance (SPR) binding studies revealed that the Pam protein itself has adhesive properties. Although Pam is produced throughout insect infection, genetic knockout does not affect either insect virulence or the ability of P. luminescens to form a symbiotic association with its host nematode, Heterorhabditis bacteriophora.


CONCLUSIONS
We studied a highly abundant protein, Pam, which is secreted in a temperature-dependent manner in P. asymbiotica. Our findings indicate that Pam plays an important role in enhancing surface attachment in insect blood. Its association with exopolysaccharide suggests it may exert its effect through mediation of EPS properties. Despite its abundance and conservation in the genus, we find no evidence for a role of Pam in either virulence or symbiosis.
Jones
Robert T
RT
Department of Biology and Biochemistry, University of Bath, Claverton Down, Bath BA27AY, UK.
Sanchez-Contreras
Maria
M
Vlisidou
Isabella
I
Amos
Matthew R
MR
Yang
Guowei
G
Muñoz-Berbel
Xavier
X
Upadhyay
Abhishek
A
Potter
Ursula J
UJ
Joyce
Susan A
SA
Ciche
Todd A
TA
Jenkins
A Toby A
AT
Bagby
Stefan
S
Ffrench-Constant
Richard H
RH
Waterfield
Nicholas R
NR
D018829:Adhesins, Bacterial / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001413:Bacillus thuringiensis / Q000235:genetics; D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001427:Bacterial Toxins / Q000235:genetics; D015180:Electrophoresis, Gel, Two-Dimensional; D016905:Gram-Negative Bacterial Infections / Q000382:microbiology; D006801:Humans; D007915:Lepidoptera / Q000382:microbiology; D009348:Nematoda / Q000382:microbiology; D020637:Photorhabdus / Q000254:growth & development / Q000302:isolation & purification / Q000472:pathogenicity / Q000502:physiology*; D011135:Polysaccharides, Bacterial / Q000378:metabolism*; D020543:Proteome / Q000032:analysis; D017386:Sequence Homology, Amino Acid; D020349:Surface Plasmon Resonance; D013559:Symbiosis; D013696:Temperature; D014774:Virulence
D018829:Adhesins, Bacterial; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D011135:Polysaccharides, Bacterial; D020543:Proteome
Biochemistry. 1998 Jul 28;37(30):10563-72
9692945
Nature. 1976 Jun 17;261(5561):552-8
934293
J Bacteriol. 2004 Oct;186(20):6928-37
15466046
Nat Biotechnol. 2001 Jul;19(7):668-72
11433280
Emerg Infect Dis. 2006 Oct;12(10):1562-4
17176572
Appl Environ Microbiol. 2002 Mar;68(3):1137-45
11872461
Annu Rev Microbiol. 1997;51:47-72
9343343
Microbiology (Reading). 2003 Jun;149(Pt 6):1581-1591
12777498
J Bacteriol. 1951 Sep;62(3):293-300
14888646
J Clin Microbiol. 1989 Jul;27(7):1594-600
2768446
Plasmid. 2004 May;51(3):246-55
15109831
J Bacteriol. 1998 Apr;180(7):1691-9
9537364
Int J Syst Bacteriol. 1999 Oct;49 Pt 4:1645-56
10555346
Appl Environ Microbiol. 2003 Apr;69(4):1890-7
12676661
Cell Microbiol. 2002 Jun;4(6):329-39
12067318
Infect Immun. 2009 Mar;77(3):1022-30
19075024
Mol Microbiol. 2003 Oct;50(1):15-27
14507360
J Mol Biol. 1996 Dec 13;264(4):784-805
8980686
Proteomics. 2006 May;6(9):2705-25
16548063
BMC Genomics. 2009 Jul 07;10:302
19583835
Proc Natl Acad Sci U S A. 2008 Oct 14;105(41):15967-72
18838673
Protein Eng. 2000 Mar;13(3):179-91
10775659
Biochemistry. 1982 Sep 28;21(20):4960-8
6291595
Bioinformatics. 2002 Jan;18(1):211-2
11836237
Microbes Infect. 2004 Feb;6(2):229-37
15049334
Cell Microbiol. 2005 Mar;7(3):363-71
15679839
Appl Environ Microbiol. 2008 Apr;74(8):2275-87
18281425
BMC Genomics. 2008 May 19;9:229
18489737
Curr Opin Microbiol. 2007 Dec;10(6):644-8
17981495
FEMS Microbiol Rev. 2003 Jan;26(5):433-56
12586390
Biochim Biophys Acta. 2005 Aug 10;1751(2):119-39
16027053
Appl Environ Microbiol. 2005 Apr;71(4):1765-74
15811999
Science. 1999 May 21;284(5418):1318-22
10334980
Nucleic Acids Res. 2004 Jul 1;32(Web Server issue):W668-73
15215473
Anal Biochem. 2000 Dec 15;287(2):252-60
11112271
J Bacteriol. 1995 Jul;177(14):4121-30
7608087
Mol Biol Rep. 2009 Apr;36(4):785-90
18409059