Evidence that putrescine acts as an extracellular signal required for swarming in Proteus mirabilis

Abstract

SummaryIn a search for Proteus mirabilis genes that were regulated by cell-to-cell signalling, a lacZ fusion ( cmr437:: mini-Tn 5lacZ ) was identified that was repressed 10-fold by a self-produced extracellular signal from wild-type cells. However, the cmr437 ::miniTn 5lacZ insertion itself led to a marked reduction in this extracellular repressing signal. The cmr437 ::miniTn 5lacZ insertion was mapped to a speA homologue in P. mirabilis. Sequence analysis indicated that a speB homologue was encoded downstream of speA . Products of the SpeA and SpeB enzymes (agmatine and putrescine) were tested for repression of cmr437::lacZ . Agmatine did not have repressing activity. However, putrescine was an effective repressing molecule at concentrations down to 30 m m m m M. A second prominent phenotype of the cmr437 ( speA )::miniTn 5lacZ insertion was a severe defect in swarming motility. This swarming defect was also observed in a strain containing a disruption of the downstream speB gene. Differentiation of the speB mutant to swarmer cells was delayed by two hours relative to wild-type cells. Furthermore, the speB mutant was unable to migrate effectively across agar surfaces and formed very closely spaced swarming rings. Exogenous putrescine restored both the normal timing of swarmer cell differentiation and the ability to migrate to speB mutants.

A Novel Putrescine Importer Required for Type 1 Pili-driven Surface Motility Induced by Extracellular Putrescine in Escherichia coli K-12

“…Furthermore, ⌬speA ⌬speC mutants can only form biofilms when the medium is supplemented with putrescine (11). In Proteus mirabilis, a common human urinary tract pathogen, putrescine acts as a cell-to-cell signaling molecule that induces differentiation into swarm cells (12). When extracellular polyamines are used as signaling molecules, bacteria require a polyamine sensor or polyamine importer because polyamines are hydrophilic molecules that cannot passively cross the plasma membrane.…”

Proteus mirabilis interkingdom swarming signals attract blow flies

“…It belongs to the group of polyamines, including putrescine, agmatine and spermidine, and is a constituent of the outer membrane of P. mirabilis. Putrescine is the product of SpeB in P. mirabilis (Sturgill and Rather, 2004), and mutations in speA (encoding arginine decarboxylase) or speB (encoding agmatine ureohydrolase) block putrescine production and result in a 2-to 3-h delay in swarmer cell differentiation (Stevenson and Rather, 2006). Adding 25 mM exogenous putrescine can completely restore the swarmer cell differentiation of the speA mutant (Stevenson and Rather, 2006).…”

“…All the chemicals except putrescine have not been associated with swarming previously, and all but the rfaL mutation have not been associated with swarming previously; hence, putrescine and the rfaL mutation confirm the effectiveness of our approach. Putrescine is an extracellular signal required for swarming in P. mirabilis (Sturgill and Rather, 2004). It belongs to the group of polyamines, including putrescine, agmatine and spermidine, and is a constituent of the outer membrane of P. mirabilis.…”

“…Hence, in addition to attracting flies, these chemicals also function as molecules that control swarming of P. mirabilis. With the exception of putrescine (Sturgill and Rather, 2004), these fly attractants have not been previously associated with swarming. We also identified seven (RfaL, UreR, Fis, HybG, ZapB, FadE and PROSTU_03490) biochemical pathways through which these attractants work by identifying the genes disrupted by the transposon mutagenesis.…”

“…With 2-mercaptoethanol and sodium sulfide: 10-100 mg ml À1 , and swormlure-2: 41 mg ml À1 (Urech et al, 2004) Sodium hydroxide L. cuprina (Dethier, 1947) NA Water: 200 mg ml À1 (Hepburn and Nolte, 1943) a Potassium hydroxide L. cuprina (Dethier, 1947) NA Water: 7.2-240 mg ml À1 (Hepburn and Nolte, 1943) a Lactic acid L. sericata, Calliphora erythrocephala (Dethier, 1947) Lactobacillus acidophilus: 0.07-0.7 mg ml À1 (Juárez Tomás et al, 2003) A total amount of 0.023-0.133 mg h À1 from human hands is attractive to mosquitoes Aedes aegypti (Smith et al, 1970) b Ammonia L. sericata (Hilker and Meiners, 2002) P. mirabilis: 0.297 mg ml À1 (Vince et al, 1973) Ammonium hydroxide: 5% (Cragg, 1950) Putrescine Calliphoridae (Wardle, 1921) P. mirabilis: 0.003-0.088 mg ml À1 (Sturgill and Rather, 2004) Water on filter paper: 0.001-1 mg ml À1 (Robacker, 2001), 1 mg attracts 70% L. sericata (this study) p-Cresol Cochliomyia, Chrysomya (Hilker and Meiners, 2002) Lactobacillus spp. : 0.8 mg ml À1 in (Yokoyama and Carlson, 1981) A total amount of 0.005-0.02 mg ml À1 used to attract mosquitoes (Culex quinquefasciatus) for oviposition (Poonam et al, 2002) b Benzoic acid Cochliomyia, Chrysomya (Hilker and Meiners, 2002) NA Swormlure-2: 41 mg ml À1 (Urech et al, 2004) Butyric acid Cochliomyia (Broce, 1980) Pig cecal bacteria: 0.053-1.057 mg ml À1 (Kobayashi and Sakata, 2006) A total amount of 0.02 mg ml À1 used as a synthetic fly attractant for Fannia femoralis (Mulla et al, 1984) Phenol Cochliomyia, Chrysomya (Hilker and Meiners, 2002) Marine bacteria: 0.1-1 mg ml À1 (Updegraff, 1949) Swormlure-2: 41 mg ml À1 used in (Urech et al, 2004) Abbreviation: NA, not applicable.…”