Table 1 Plasmids used in this study

pBSMul1

E. coli–B. subtilis shuttle vector, P_HpaII, secretion signal (SPlipA), ColE1 repB Km^rAmp^r

[22]

pET22-sfGFP1-10

pET22b(+) containing the truncated sfGFP1-10 gen under control of P_T7

[31]

pEBP41

E. coli–B. subtilis–P. putida shuttle vector, P_T7, P_xyl, Gm^r, GFPmut3

[29]

pEBP41-NdeI

pEBP41 with deleted NdeI site within the GFPmut3 gene by QuikChange PCR^® using the primers P1 and P2

This study

pBSMul1(SPBox)-SPxxx-cut-11

Signal peptide (SP) library based on pBSMul1 containing HindIII–XbaI inserts of the cutinase cut of F. solani pisi fused to a GFP11 tag and with different signal peptides (SPepr, SPpel, SPbsn)

[31]

pBSMul1(SPBox)-SPxxx-EXLX1-11

Signal peptide (SP) library based on pBSMul1 containing HindIII–XbaI inserts of the swollenin EXLX1 of B. subtilis fused to a GFP11 tag and with different signal peptides (SPepr, SPpel, SPbsn)

[31]

Standard expression plasmids (based on pBSMul1 with a 4 nucleotide spacer)

 pBS4nt-GFPmut3

pBSMul1 containing a 723 bp NdeI–XbaI GFPmut3 fragment amplified from pEBP41-NdeI with primers P3/P4

This study

 pBS4nt-GUS

pBSMul1 containing a 1828 bp NdeI–XbaI (uidA) fragment amplified from E. coli DH5α genome with primers P5/P6

This study

 pBS4nt-SPepr-cut-11

pBSMul1 containing an 845 bp NdeI–XbaI SPepr-cut-11 fragment amplified from SP library using primers P7/P10

This study

 pBS4nt-SPpel-cut-11

pBSMul1 containing an 827 bp NdeI–XbaI SPpel-cut-11 fragment amplified from SP library using primers P8/P10

This study

 pBS4nt-SPbsn-cut-11

pBSMul1 containing an 848 bp NdeI–XbaI SPbsn-cut-11 fragment amplified from SP library using primers P9/P10

This study

 pBS4nt-SPepr-EXLX1-11

pBSMul1 containing an 824 bp NdeI–XbaI SPEXLX1-cut-11 fragment amplified from SP library using primers P7/P10

This study

 pBS4nt-SPpel-EXLX1-11

pBSMul1 containing an 806 bp NdeI–XbaI SPpel-EXLX1-11 fragment amplified from SP library using primers P8/P10

This study

 pBS4nt-SPbsn-EXLX1-11

pBSMul1 containing an 827 bp NdeI–XbaI SPbsn-EXLX1-11 fragment amplified from SP library using primers P9/P10

This study

Expression plasmids with extended spacers

 pBSxnt-Y

Spacers ranging in length from 5 to 12 nucleotides (xnt) by insertion of adenosines for all above mentioned plasmids (Y: -GFPmut3, -GUS, -SPepr-cut-11, -SPpel-cut-11, -SPbsn-cut-11, -SPepr-EXLX1-11, -SPpel-EXLX1-11, -SPbsn-EXLX1-11)

This study

 pBSxnt-SPepr-cut-11_start1

pBSxnt-SPepr-cut-11 with the second putative translational start codon ATG exchanged by ACG

This study

 pBSxnt-SPepr-cut-11_start2

pBSxnt-SPepr-cut-11 with the first translational start codon ATG exchanged by ACG

This study

Spacer sequence library

 pBS7nt-4N-GFPmut3

Spacer library based on pBS7nt-GFPmut3 containing the 7nt long spacer sequence 5′-NNNNCAT-3′ inserted by QuikChange PCR^® and primers P27/P28

This study

 pBS7nt-4N-SPpel-cut-11

Spacer library based on pBS7nt-SPpel-cut-11 containing the 7nt long spacer sequence 5′-NNNNCAT-3′ inserted by QuikChange PCR^® and primers P29/P30

This study