Phylogeny and fitness of Vibrio fischeri from the light organs of Euprymna scolopes in two Oahu,Hawaii populations

The evolutionary relationship among Vibrio fischeri isolates obtained from the light organs of Euprymna scolopes collected around Oahu, Hawaii, were examined in this study. Phylogenetic reconstructions based on a concatenation of fragments of four housekeeping loci (recA, mdh, katA, pyrC) identified one monophyletic group (‘Group-A'') of V. fischeri from Oahu. Group-A V. fischeri strains could also be identified by a single DNA fingerprint type. V. fischeri strains with this fingerprint type had been observed to be at a significantly higher abundance than other strains in the light organs of adult squid collected from Maunalua Bay, Oahu, in 2005. We hypothesized that these previous observations might be related to a growth/survival advantage of the Group-A strains in the Maunalua Bay environments. Competition experiments between Group-A strains and non-Group-A strains demonstrated an advantage of the former in colonizing juvenile Maunalua Bay hosts. Growth and survival assays in Maunalua Bay seawater microcosms revealed a reduced fitness of Group-A strains relative to non-Group-A strains. From these results, we hypothesize that there may exist trade-offs between growth in the light organ and in seawater environments for local V. fischeri strains from Oahu. Alternatively, Group-A V. fischeri may represent an example of rapid, evolutionarily significant, specialization of a horizontally transmitted symbiont to a local host population.     

Ecological Diversification of Vibrio fischeri Serially Passaged for 500 Generations in Novel Squid Host Euprymna tasmanica

Vibrio fischeri isolated from Euprymna scolopes (Cephalopoda: Sepiolidae) was used to create 24 lines that were serially passaged through the non-native host Euprymna tasmanica for 500 generations. These derived lines were characterized for biofilm formation, swarming motility, carbon source utilization, and in vitro bioluminescence. Phenotypic assays were compared between “ES” (E. scolopes) and “ET” (E. tasmanica) V. fischeri wild isolates to determine if convergent evolution was apparent between E. tasmanica evolved lines and ET V. fischeri. Ecological diversification was observed in utilization of most carbon sources examined. Convergent evolution was evident in motility, biofilm formation, and select carbon sources displaying hyperpolymorphic usage in V. fischeri. Convergence in bioluminescence (a 2.5-fold increase in brightness) was collectively evident in the derived lines relative to the ancestor. However, dramatic changes in other properties—time points and cell densities of first light emission and maximal light output and emergence of a lag phase in growth curves of derived lines—suggest that increased light intensity per se was not the only important factor. Convergent evolution implies that gnotobiotic squid light organs subject colonizing V. fischeri to similar selection pressures. Adaptation to novel hosts appears to involve flexible microbial metabolism, establishment of biofilm and swarmer V. fischeri ecotypes, and complex changes in bioluminescence. Our data demonstrate that numerous alternate fitness optima or peaks are available to V. fischeri in host adaptive landscapes, where novel host squids serve as habitat islands. Thus, V. fischeri founder flushes occur during the initiation of light organ colonization that ultimately trigger founder effect diversification.     

Relative Contributions of Vibrio Polysaccharide and Quorum Sensing to the Resistance of Vibrio cholerae to Predation by Heterotrophic Protists

Protozoan grazing is a major mortality factor faced by bacteria in the environment. Vibrio cholerae, the causative agent of the disease cholera, is a natural inhabitant of aquatic ecosystems, and its survival depends on its ability to respond to stresses, such as predation by heterotrophic protists. Previous results show that grazing pressure induces biofilm formation and enhances a smooth to rugose morphotypic shift, due to increased expression of Vibrio polysaccharide (VPS). In addition to negatively controlling vps genes, the global quorum sensing (QS) regulator, HapR, plays a role in grazing resistance as the ΔhapR strain is efficiently consumed while the wild type (WT) is not. Here, the relative and combined contributions of VPS and QS to grazing resistance were investigated by exposing VPS and HapR mutants and double mutants in VPS and HapR encoding genes at different phases of biofilm development to amoeboid and flagellate grazers. Data show that the WT biofilms were grazing resistant, the VPS mutants were less resistant than the WT strain, but more resistant than the QS mutant strain, and that QS contributes to grazing resistance mainly in mature biofilms. In addition, grazing effects on biofilms of mixed WT and QS mutant strains were investigated. The competitive fitness of each strain in mixed biofilms was determined by CFU and microscopy. Data show that protozoa selectively grazed the QS mutant in mixed biofilms, resulting in changes in the composition of the mixed community. A small proportion of QS mutant cells which comprised 4% of the mixed biofilm biovolume were embedded in grazing resistant WT microcolonies and shielded from predation, indicating the existence of associational protection in mixed biofilms.     

Grazing resistance of Pseudomonas aeruginosa biofilms depends on type of protective mechanism, developmental stage and protozoan feeding mode

In a previous study we identified microcolony formation and inhibitor production as the major protective mechanisms of Pseudomonas aeruginosa biofilms against flagellate grazing. Here we compared the efficacy of these two key protective mechanisms by exposing biofilms of the non-toxic alginate overproducing strain PDO300 and the wild-type toxic strain PAO1 to a range of feeding types commonly found in the succession of protozoans associated with natural biofilms. Alginate-mediated microcolony formation conferred effective protection for strain PDO300 against the suspension feeding flagellate Bodo saltans and, as reported earlier, the surface feeding flagellate Rhynchomonas nasuta, both of which are considered as early biofilm colonizers. However, microcolonies of mature PDO300 biofilms were highly susceptible to late biofilm colonizers, the surface-feeding amoeba Acanthamoeba polyphaga and the planktonic ciliate Tetrahymena sp., resulting in a significant reduction of biofilm biomass. Mature biofilms of strain PAO1 inhibited growth of flagellates and A. polyphaga while the grazing activity of Tetrahymena sp. remained unaffected. Our findings suggest that inhibitor production of mature P. aeruginosa biofilms is effective against a wider range of biofilm-feeding predators while microcolony-mediated protection is only beneficial in the early stages of biofilm formation.     

Biofilm-Forming Abilities of Shiga Toxin-Producing Escherichia coli Isolates Associated with Human Infections

Forming biofilms may be a survival strategy of Shiga toxin-producing Escherichia coli to enable it to persist in the environment and the food industry. Here, we evaluate and characterize the biofilm-forming ability of 39 isolates of Shiga toxin-producing Escherichia coli isolates recovered from human infection and belonging to seropathotypes A, B, or C. The presence and/or production of biofilm factors such as curli, cellulose, autotransporter, and fimbriae were investigated. The polymeric matrix of these biofilms was analyzed by confocal microscopy and by enzymatic digestion. Cell viability and matrix integrity were examined after sanitizer treatments. Isolates of the seropathotype A (O157:H7 and O157:NM), which have the highest relative incidence of human infection, had a greater ability to form biofilms than isolates of seropathotype B or C. Seropathotype A isolates were unique in their ability to produce cellulose and poly-N-acetylglucosamine. The integrity of the biofilms was dependent on proteins. Two autotransporter genes, ehaB and espP, and two fimbrial genes, z1538 and lpf2, were identified as potential genetic determinants for biofilm formation. Interestingly, the ability of several isolates from seropathotype A to form biofilms was associated with their ability to agglutinate yeast in a mannose-independent manner. We consider this an unidentified biofilm-associated factor produced by those isolates. Treatment with sanitizers reduced the viability of Shiga toxin-producing Escherichia coli but did not completely remove the biofilm matrix. Overall, our data indicate that biofilm formation could contribute to the persistence of Shiga toxin-producing Escherichia coli and specifically seropathotype A isolates in the environment.     

Acidic pH Strongly Enhances In Vitro Biofilm Formation by a Subset of Hypervirulent ST-17 Streptococcus agalactiae Strains

Streptococcus agalactiae, also known as group B Streptococcus (GBS), is a primary colonizer of the anogenital mucosa of up to 40% of healthy women and an important cause of invasive neonatal infections worldwide. Among the 10 known capsular serotypes, GBS type III accounts for 30 to 76% of the cases of neonatal meningitis. In recent years, the ability of GBS to form biofilm attracted attention for its possible role in fitness and virulence. Here, a new in vitro biofilm formation protocol was developed to guarantee more stringent conditions, to better discriminate between strong-, low-, and non-biofilm-forming strains, and to facilitate interpretation of data. This protocol was used to screen the biofilm-forming abilities of 366 GBS clinical isolates from pregnant women and from neonatal infections of different serotypes in relation to medium composition and pH. The results identified a subset of isolates of serotypes III and V that formed strong biofilms under acidic conditions. Importantly, the best biofilm formers belonged to serotype III hypervirulent clone ST-17. Moreover, the abilities of proteinase K to strongly inhibit biofilm formation and to disaggregate mature biofilms suggested that proteins play an essential role in promoting GBS biofilm initiation and contribute to biofilm structural stability.     

In Vitro Modulation of E. coli Community Behavior and Human Innate Immune System by Lantibiotic Nisin

Biofilms are microbial communities with genetically divergent microorganisms. Such communal behavior is known to provide survival benefit to the unicellular organisms in adverse conditions. Pathogenicity of opportunistic bacterial pathogens largely depends on their success in proper quorum establishment and biofilm formation. Thus molecules causing quorum-sensing attenuation, preventing the biofilm formation or instigating preformed biofilm dislodgement could serve as attractive drugs/drug supplements. Here we investigate the effect of nisin??type A lantibiotic naturally produced by Lactococcus lactis??on laboratory developed Escherichia coli biofilms and on isolated human neutrophils. Activity evaluation was done on the biofilms of clinical isolates of E. coli, developed on glass slides in a simple static bioreactor design. Nisin not only inhibited the formation but also effectively dislodged the preformed E. coli biofilms developed on glass surfaces. Presence of nisin also demonstrated a significant decrease in the expression of E. coli virulence factors viz. hemolysin and curli expression. The microorganisms dislodged from the biofilms and set free in the circulation of infected host might later reassociate to form new biofilms after nisin clearance from circulation. Thus complete eradication of infective bacterium will depend on stimulatory effect of nisin (if any) on human immune system cells. Therefore modulation of human neutrophil activity by nisin was also evaluated. Presence of nisin induced neutrophil extracellular trap (NET) formation or NETosis in a manner similar to that demonstrated by LPS (lipopolysaccharide) in vitro. Our results thus present nisin as a plausible molecule to be used in treatment of chronic bacterial infections as it indicated increased fitness for the same.     

Environmental Determinants of Vibrio cholerae Biofilm Development

Vibrio cholerae is a versatile bacterium that flourishes in diverse environments, including the human intestine, rivers, lakes, estuaries, and the ocean. Surface attachment is believed to be essential for colonization of all of these natural environments. Previous studies have demonstrated that the vps genes, which encode proteins required for exopolysaccharide synthesis and transport, are required for V. cholerae biofilm development in Luria-Bertani broth. In this work, we showed that V. cholerae forms vps-dependent biofilms and vps-independent biofilms. The vps-dependent and -independent biofilms differ in their environmental activators and in architecture. Our results suggest that environmental activators of vps-dependent biofilm development are present in freshwater, while environmental activators of vps-independent biofilm development are present in seawater. The distinct environmental requirements for the two modes of biofilm development suggest that vps-dependent biofilm development and vps-independent biofilm development may play distinct roles in the natural environment.     

Microbial Exopolymers Link Predator and Prey in a Model Yeast Biofilm System

Protistan grazing on biofilms is potentially an important conduit enabling energy flow between microbial trophic levels. Contrary to the widely held assumption that protistan feeding primarily involves ingestion of biofilm cells, with negative consequences for the biofilm, this study demonstrated preferential grazing on the noncellular biofilm matrix by a ciliate, with selective ingestion of yeast and bacterial cells of planktonic origin over attached and biofilm-derived planktonic cells. Introducing a ciliate to two biofilm-forming Cryptococcus species, as well as two bacterial species in a model biofilm system, fluorescent probes were applied to determine ingestion of cellular and noncellular biofilm fractions. Fluoromicroscopy, as well as photometric quantification, confirmed that protistan grazing enhanced yeast biofilm metabolism, and an increase in biofilm biomass and viability. We propose that the extracellular polymeric matrix of biofilms may act as an interface regulating interaction between predator and prey, while serving as source of nutrients and energy for protists.     

Detection of the Light Organ Symbiont, Vibrio fischeri, in Hawaiian Seawater by Using lux Gene Probes

Symbiotic bacteria that inhabit the light-emitting organ of the Hawaiian squid Euprymna scolopes are distinctive from typical Vibrio fischeri organisms in that they are not visibly luminous when grown in laboratory culture. Therefore, the abundance of these bacteria in seawater samples cannot be estimated simply by identifying them among luminous colonies that arise on nutrient agar plates. Instead, we have used luxR and polymerase chain reaction generated luxA gene probes to identify both luminous and non-visibly luminous V. fischeri colonies by DNA-DNA hybridization. The probes were specific, hybridizing at least 50 to 100 times more strongly to immobilized DNAs from V. fischeri strains than to those of pure cultures of other related species. Thus, even non-visibly luminous V. fischeri colonies could be identified among colonies obtained from natural seawater samples by their probe-positive reaction. Bacteria in seawater samples, obtained either within or distant from squid habitats, were collected on membrane filters and incubated until colonies appeared. The filters were then observed for visibly luminous V. fischeri colonies and hybridized with the lux gene probes to determine the number of total V. fischeri colonies (both luminous and non-visibly luminous). We detected no significant differences in the abundance of luminous V. fischeri CFU in any of the water samples observed (≤1 to 3 CFU/100 ml). However, probe-positive colonies of V. fischeri (up to 900 CFU/100 ml) were found only in seawater collected from within the natural habitats of the squids. A number of criteria were used to confirm that these probe-positive strains were indistinguishable from symbiotic V. fischeri. Therefore, the luxA and luxR gene probes were species specific and gave a reliable estimate of the number of culturable V. fischeri colonies in natural water samples.     

The pathogenic actinobacterium Rhodococcus equi: what's in a name?

A key regulatory decision for many bacteria is the switch between biofilm formation and motile dispersal, and this dynamic is well illustrated in the light‐organ symbiosis between the bioluminescent bacterium Vibrio fischeri and the Hawaiian bobtail squid. Biofilm formation mediated by the syp gene cluster helps V. fischeri transition from a dispersed planktonic lifestyle to a robust aggregate on the surface of the nascent symbiotic organ. However, the bacteria must then swim to pores and down into the deeper crypt tissues that they ultimately colonize. A number of positive and negative regulators control syp expression and biofilm formation, but until recently the environmental inputs controlling this clash between opposing regulatory mechanisms have been unclear. Thompson et al. have now shown that Syp‐mediated biofilms can be repressed by a well‐known host‐derived molecule: nitric oxide. This regulation is accomplished by the NO sensor HnoX exerting control over the biofilm regulator HahK. The discoveries reported here by Thompson et al. cast new light on a critical early stage of symbiotic initiation in the V. fischeri‐squid model symbiosis, and more broadly it adds to a growing understanding of the role(s) that NO and HnoX play in biofilm regulation by many bacteria.     

Characterization of Biofilm Formation in [Pasteurella] pneumotropica and [Actinobacillus] muris Isolates of Mouse Origin

[Pasteurella] pneumotropica biotypes Jawetz and Heyl and [Actinobacillus] muris are the most prevalent Pasteurellaceae species isolated from laboratory mouse. However, mechanisms contributing to their high prevalence such as the ability to form biofilms have not been studied yet. In the present investigation we analyze if these bacterial species can produce biofilms in vitro and investigate whether proteins, extracellular DNA and polysaccharides are involved in the biofilm formation and structure by inhibition and dispersal assays using proteinase K, DNase I and sodium periodate. Finally, the capacity of the biofilms to confer resistance to antibiotics is examined. We demonstrate that both [P.] pneumotropica biotypes but not [A.] muris are able to form robust biofilms in vitro, a phenotype which is widely spread among the field isolates. The biofilm inhibition and dispersal assays by proteinase and DNase lead to a strong inhibition in biofilm formation when added at the initiation of the biofilm formation and dispersed pre-formed [P.] pneumotropica biofilms, revealing thus that proteins and extracellular DNA are essential in biofilm formation and structure. Sodium periodate inhibited the bacterial growth when added at the beginning of the biofilm formation assay, making difficult the assessment of the role of β-1,6-linked polysaccharides in the biofilm formation, and had a biofilm stimulating effect when added on pre-established mature biofilms of [P.] pneumotropica biotype Heyl and a majority of [P.] pneumotropica biotype Jawetz strains, suggesting that the presence of β-1,6-linked polysaccharides on the bacterial surface might attenuate the biofilm production. Conversely, no effect or a decrease in the biofilm quantity was observed by biofilm dispersal using sodium periodate on further biotype Jawetz isolates, suggesting that polysaccharides might be incorporated in the biofilm structure. We additionally show that [P.] pneumotropica cells enclosed in biofilms were less sensitive to treatment with amoxicillin and enrofloxacin than planktonic bacteria. Taken together, these findings provide a first step in understanding of the biofilm mechanisms in [P.] pneumotropica, which might contribute to elucidation of colonization and pathogenesis mechanisms for these obligate inhabitants of the mouse mucosa.     

Gene-Swapping Mediates Host Specificity among Symbiotic Bacteria in a Beneficial Symbiosis

Environmentally acquired beneficial associations are comprised of a wide variety of symbiotic species that vary both genetically and phenotypically, and therefore have differential colonization abilities, even when symbionts are of the same species. Strain variation is common among conspecific hosts, where subtle differences can lead to competitive exclusion between closely related strains. One example where symbiont specificity is observed is in the sepiolid squid-Vibrio mutualism, where competitive dominance exists among V. fischeri isolates due to subtle genetic differences between strains. Although key symbiotic loci are responsible for the establishment of this association, the genetic mechanisms that dictate strain specificity are not fully understood. We examined several symbiotic loci (lux-bioluminescence, pil = pili, and msh-mannose sensitive hemagglutinin) from mutualistic V. fischeri strains isolated from two geographically distinct squid host species (Euprymna tasmanica-Australia and E. scolopes-Hawaii) to determine whether slight genetic differences regulated host specificity. Through colonization studies performed in naïve squid hatchlings from both hosts, we found that all loci examined are important for specificity and host recognition. Complementation of null mutations in non-native V. fischeri with loci from the native V. fischeri caused a gain in fitness, resulting in competitive dominance in the non-native host. The competitive ability of these symbiotic loci depended upon the locus tested and the specific squid species in which colonization was measured. Our results demonstrate that multiple bacterial genetic elements can determine V. fischeri strain specificity between two closely related squid hosts, indicating how important genetic variation is for regulating conspecific beneficial interactions that are acquired from the environment.     

Dominance of Vibrio fischeri in Secreted Mucus outside the Light Organ of Euprymna scolopes: the First Site of Symbiont Specificity

Previous studies of the Euprymna scolopes-Vibrio fischeri symbiosis have demonstrated that, during colonization, the hatchling host secretes mucus in which gram-negative environmental bacteria amass in dense aggregations outside the sites of infection. In this study, experiments with green fluorescent protein-labeled symbiotic and nonsymbiotic species of gram-negative bacteria were used to characterize the behavior of cells in the aggregates. When hatchling animals were exposed to 10³ to 10⁶ V. fischeri cells/ml added to natural seawater, which contains a mix of approximately 10⁶ nonspecific bacterial cells/ml, V. fischeri cells were the principal bacterial cells present in the aggregations. Furthermore, when animals were exposed to equal cell numbers of V. fischeri (either a motile or a nonmotile strain) and either Vibrio parahaemolyticus or Photobacterium leiognathi, phylogenetically related gram-negative bacteria that also occur in the host's habitat, the symbiont cells were dominant in the aggregations. The presence of V. fischeri did not compromise the viability of these other species in the aggregations, and no significant growth of V. fischeri cells was detected. These findings suggested that dominance results from the ability of V. fischeri either to accumulate or to be retained more effectively within the mucus. Viability of the V. fischeri cells was required for both the formation of tight aggregates and their dominance in the mucus. Neither of the V. fischeri quorum-sensing compounds accumulated in the aggregations, which suggested that the effects of these small signal molecules are not critical to V. fischeri dominance. Taken together, these data provide evidence that the specificity of the squid-vibrio symbiosis begins early in the interaction, in the mucus where the symbionts aggregate outside of the light organ.     

Protozoan grazing and its impact upon population dynamics in biofilm communities

AIMS: To determine the impact of protozoan grazing on the population dynamics of a multispecies bacterial biofilm community. METHODS AND RESULTS: Grazing by Acanthamoeba castellanii and the ciliate Colpoda maupasi upon biofilm and planktonic communities, composed of Klebsiella pneumoniae, Pseudomonas fluorescens and Staphylococcus epidermidis was investigated. Biofilms were formed using glass coverslips, held in a carousel device, as substrata for biofilm formation or in glass flow cells. The predatory effects of the amoeba were generally confined to the biofilm, where grazing rates corresponded to losses from the biofilm equivalent to ca 30,000 biofilm cells cm(-2) h(-1), with the amoeba becoming an integral part of the community. C. maupasi reduced the thickness of mature multispecies biofilms at steady-state from 500 to <200 microm. CONCLUSIONS: We report that the presence of the protozoa A. castellanii and C. maupasi markedly influence population dynamics within defined biofilm communities. SIGNIFICANCE AND IMPACT OF THE STUDY: The current study dispels the popular opinion that biofilms are protected against predation by protozoa. A. castellanii clearly has the capacity to graze mixed biofilm communities and to become integrally associated with them, whereas the ciliate C. maupasi reduced biofilm thickness by up to 60%.     

In situ grazing resistance of Vibrio cholerae in the marine environment

Previous laboratory experiments revealed that Vibrio cholerae A1552 biofilms secrete an antiprotozoal factor that prevents Rhynchomonas nasuta from growing and thus prevents grazing losses. The antiprotozoal factor is regulated by the quorum-sensing response regulator, HapR. Here, we investigate whether the antiprotozoal activity is ecologically relevant. Experiments were conducted in the field as well as under field-like conditions in the laboratory to assess the grazing resistance of V. cholerae A1552 and N16961 (natural frameshift mutation in hapR) biofilms to R. nasuta and Cafeteria roenbergensis. In laboratory experiments exposing the predators to V. cholerae grown in seawater containing high and low glucose concentrations, we determined that V. cholerae biofilms showed increased resistance towards grazing by both predators as glucose levels decreased. The relative resistance of the V. cholerae strains to the grazers under semi-field conditions was similar to that observed in situ. Therefore, the antipredator defense is environmentally relevant and not lost when biofilms are grown in an open system in the marine environment. The hapR mutant still exhibited some resistance to both predators and this suggests that V. cholerae may coordinate antipredator defenses by a combination of density-dependent regulation and environmental sensing to protect itself from predators in its natural habitat.     

LapG mediates biofilm dispersal in Vibrio fischeri by controlling maintenance of the VCBS-containing adhesin LapV

Efficient symbiotic colonization of the squid Euprymna scolopes by the bacterium Vibrio fischeri depends on bacterial biofilm formation on the surface of the squid’s light organ. Subsequently, the bacteria disperse from the biofilm via an unknown mechanism and enter through pores to reach the interior colonization sites. Here, we identify a homolog of Pseudomonas fluorescens LapG as a dispersal factor that promotes cleavage of a biofilm-promoting adhesin, LapV. Overproduction of LapG inhibited biofilm formation and, unlike the wild-type parent, a ΔlapG mutant formed biofilms in vitro. Although V. fischeri encodes two putative large adhesins, LapI (near lapG on chromosome II) and LapV (on chromosome I), only the latter contributed to biofilm formation. Consistent with the Pseudomonas Lap system model, our data support a role for the predicted c-di-GMP-binding protein LapD in inhibiting LapG-dependent dispersal. Furthermore, we identified a phosphodiesterase, PdeV, whose loss promotes biofilm formation similar to that of the ΔlapG mutant and dependent on both LapD and LapV. Finally, we found a minor defect for a ΔlapD mutant in initiating squid colonization, indicating a role for the Lap system in a relevant environmental niche. Together, these data reveal new factors and provide important insights into biofilm dispersal by V. fischeri.     

Genetic Dissection of an Exogenously Induced Biofilm in Laboratory and Clinical Isolates of E. coli

Microbial biofilms are a dominant feature of many human infections. However, developing effective strategies for controlling biofilms requires an understanding of the underlying biology well beyond what currently exists. Using a novel strategy, we have induced formation of a robust biofilm in Escherichia coli by utilizing an exogenous source of poly-N-acetylglucosamine (PNAG) polymer, a major virulence factor of many pathogens. Through microarray profiling of competitive selections, carried out in both transposon insertion and over-expression libraries, we have revealed the genetic basis of PNAG-based biofilm formation. Our observations reveal the dominance of electrostatic interactions between PNAG and surface structures such as lipopolysaccharides. We show that regulatory modulation of these surface structures has significant impact on biofilm formation behavior of the cell. Furthermore, the majority of clinical isolates which produced PNAG also showed the capacity to respond to the exogenously produced version of the polymer.