Genome-wide analysis of group a streptococci reveals a mutation that modulates global phenotype and disease specificity.

Many human pathogens produce phenotypic variants as a means to circumvent the host immune system and enhance survival and, as a potential consequence, exhibit increased virulence. For example, it has been known for almost 90 y that clinical isolates of the human bacterial pathogen group A streptococci (GAS) have extensive phenotypic heterogeneity linked to variation in virulence. However, the complete underlying molecular mechanism(s) have not been defined. Expression microarray analysis of nine clinical isolates identified two fundamentally different transcriptomes, designated pharyngeal transcriptome profile (PTP) and invasive transcriptome profile (ITP). PTP and ITP GAS differed in approximately 10% of the transcriptome, including at least 23 proven or putative virulence factor genes. ITP organisms were recovered from skin lesions of mice infected subcutaneously with PTP GAS and were significantly more able to survive phagocytosis and killing by human polymorphonuclear leukocytes. Complete genome resequencing of a mouse-derived ITP GAS revealed that the organism differed from its precursor by only a 7-bp frameshift mutation in the gene (covS) encoding the sensor kinase component of a two-component signal transduction system implicated in virulence. Genetic complementation, and sequence analysis of covR/S in 42 GAS isolates confirmed the central role of covR/S in transcriptome, exoproteome, and virulence modulation. Genome-wide analysis provides a heretofore unattained understanding of phenotypic variation and disease specificity in microbial pathogens, resulting in new avenues for vaccine and therapeutics research

Perspectives on the Function of Behaviors Synchronized with Calling in Female Killer Whales, Orcinus orca: Patterns of Bubbling and Nodding in Bouts

In odontocetes, synchronous visible displays accompany a small proportion of vocalizations but the function of these multimodal signals is still unclear.  Bouts of stereotyped pulsed calls were collected from two adult female killer whales ( Orcinus orca ) concurrently with behavioral observations and the incidence of two synchronous behaviors, bubble streams and nodding, were measured.  Thirty-four hours of focal individual data were collected in the presence of dependent calves in 1993 and 1994.  Overall, 471 pulsed calls were attributed to the two subjects using synchronous behaviors or independent cues (proximity, localization by ear in air).  Both subjects used the same stereotyped pulsed call repertoire and they ordered calls within bouts similarly, despite dissimilar previous histories.  Both nodding and bubble streams were disproportionately associated with a subset of stereotyped pulsed calls, but the subset was different for the two behaviors.  General Linear Model analysis was used to predict the relative odds that the subjects would be swimming with calves given call class and attribution cue.  Bubbling was not associated with significant odds that a subject would be swimming with one or more calves, but nodding was associated with significantly higher odds and resting calls with lower odds.  Given these observations, synchronous behaviors in the presence of calves could function in one or more of the following ways: altering the signal value of calls, emphasizing an aspect of the social context, and facilitating learning.  All are possibilities at the interface between cognition and communication that would have interested Stan Kuczaj

Perspectives on the Function of Behaviors Synchronized with Calling in Female Killer Whales, Orcinus orca: Patterns of Bubbling and Nodding in Bouts

In odontocetes, synchronous visible displays accompany a small proportion of vocalizations but the function of these multimodal signals is still unclear.  Bouts of stereotyped pulsed calls were collected from two adult female killer whales (Orcinus orca) concurrently with behavioral observations and the incidence of two synchronous behaviors, bubble streams and nodding, were measured.  Thirty-four hours of focal individual data were collected in the presence of dependent calves in 1993 and 1994.  Overall, 471 pulsed calls were attributed to the two subjects using synchronous behaviors or independent cues (proximity, localization by ear in air).  Both subjects used the same stereotyped pulsed call repertoire and they ordered calls within bouts similarly, despite dissimilar previous histories.  Both nodding and bubble streams were disproportionately associated with a subset of stereotyped pulsed calls, but the subset was different for the two behaviors.  General Linear Model analysis was used to predict the relative odds that the subjects would be swimming with calves given call class and attribution cue.  Bubbling was not associated with significant odds that a subject would be swimming with one or more calves, but nodding was associated with significantly higher odds and resting calls with lower odds.  Given these observations, synchronous behaviors in the presence of calves could function in one or more of the following ways: altering the signal value of calls, emphasizing an aspect of the social context, and facilitating learning.  All are possibilities at the interface between cognition and communication that would have interested Stan Kuczaj

Technology-based approaches to managing cotton bollworm in Bt Cotton

The bollworm (Helicoverpa zea), also known as the corn earworm, is considered the most economicallydamaging caterpillar pest in Texas and Mid-southern U.S. cotton production. The use of Bt expressing cottonvarieties has allowed for successful control of lepidopteran pests such as the tobacco budworm (Chlorideavirescens) for over two decades and led to the complete eradication of pink bollworm (Pectinophoragossypiella) in the U.S. Despite successfully introducing Bt cotton varieties for these pests, injury frombollworm can still be observed in all Bt cotton varieties, though injury is reduced, especially when multiple Bt toxins are expressed.Chase Floyd (University of Missouri); David Kerns (Texas A and M); Whitney Crow, Don Cook, Tyler Towles, Jeff Gore, Angus Catchot and Fred Musser (Mississippi State University); Ben Thrash, Nick Bateman, Gus Lorenz and Glenn Studebaker (University of Arkansas); Sebe Brown and Scott Stewart (University of Tennessee)

A Chemokine-Degrading Extracellular Protease Made by Group A Streptococcus Alters Pathogenesis by Enhancing Evasion of the Innate Immune Response▿ †

Circumvention of the host innate immune response is critical for bacterial pathogens to infect and cause disease. Here we demonstrate that the group A Streptococcus (GAS; Streptococcus pyogenes) protease SpyCEP (S. pyogenes cell envelope protease) cleaves granulocyte chemotactic protein 2 (GCP-2) and growth-related oncogene alpha (GROα), two potent chemokines made abundantly in human tonsils. Cleavage of GCP-2 and GROα by SpyCEP abrogated their abilities to prime neutrophils for activation, detrimentally altering the innate immune response. SpyCEP expression is negatively regulated by the signal transduction system CovR/S. Purified recombinant CovR bound the spyCEP gene promoter region in vitro, indicating direct regulation. Immunoreactive SpyCEP protein was present in the culture supernatants of covR/S mutant GAS strains but not in supernatants from wild-type strains. However, wild-type GAS strains do express SpyCEP, where it is localized to the cell wall. Strain MGAS2221, an organism representative of the highly virulent and globally disseminated M1T1 GAS clone, differed significantly from its isogenic spyCEP mutant derivative strain in a mouse soft tissue infection model. Interestingly, and in contrast to previous studies, the isogenic mutant strain generated lesions of larger size than those formed following infection with the parent strain. The data indicate that SpyCEP contributes to GAS virulence in a strain- and disease-dependent manner

Differential Gene Expression of ITP and PTP GAS

<div><p>(A) Principal component analysis plot showing transcriptome differences between invasive (red) and pharyngeal (blue) isolates. Principal component analysis assesses the variance in a dataset in terms of principal components. The two most significant principal components are displayed on the x- and y-axes. Ellipses (calculated using 2X standard deviation for each gene per group) have been superimposed to highlight group differences between ITP and PTP strains. Numbered data points refer to the MGAS strain number from which the RNA sample was isolated. The percentages of the total variation that are accounted for by the 1st and 2nd principal components are shown on the x- and y-axes labels.</p><p>(B) Log₁₀-fold transcript differences between the three ITP and six PTP isolates shown in (A) for select virulence genes and virulence gene regulators. Genes that are expressed higher in ITP isolates are shown in red; those expressed higher in PTP isolates are shown in blue. All genes shown are statistically significant (<i>t</i>-test followed by a false discovery rate correction, <i>Q</i> < 0.05).</p></div

Mouse Passage Results in Recovery of ITP Derivatives from Infecting PTP GAS

<div><p>(A) Western immunoblots of supernatant proteins obtained from overnight cultures of ITP and PTP GAS isolates, before and after mouse passage. The amount of immunoreactive SpeA, SpeB, SLO/SPN, Spd3, and Mac was unaffected by mouse passage of the ITP strain MGAS5005, whereas they were affected by all spleen and some lesion-isolated GAS after mouse passage of the PTP GAS isolate MGAS2221. Strains with a mucoid colony morphology are indicated with an asterisk (*), while nonmucoid strains are indicated by a hash (#).</p><p>(B) Principal component analysis plot portraying PTP to ITP transition for several mouse-passaged derivatives of strain MGAS2221. The 2221 NM (green) and 2221 M (purple) data points are mouse-passaged derivatives of strain MGAS2221 with distinct nonmucoid and mucoid colony morphologies, respectively. The 5005 M (orange) data points are mouse-passaged derivatives of strain MGAS5005 that retain the mucoid colony morphology of the parental strain. Ellipses (calculated using 2X standard deviation for each gene per group) have been superimposed to highlight differences between ITP and PTP GAS. The percentages of the total variation that are accounted for by the 1st and 2nd principal components are shown on the x- and y-axes labels.</p><p>(C) Log₁₀-fold differences in transcripts for select virulence genes and virulence gene regulators between all the PTP and ITP strains shown in (B). Genes expressed higher in ITP derivatives are shown in red; those expressed higher in PTP derivatives are shown in blue. RNA was isolated from bacteria grown to the exponential phase of growth in THY media. All genes shown are statistically significant as assessed by a <i>t</i>-test followed by a false discovery rate correction of <i>Q</i> < 0.05.</p></div

Differential Virulence of ITP and PTP GAS in Mouse Models of Invasive Disease

<div><p>(A) ITP GAS are significantly more virulent than PTP GAS in a mouse model of bacteremia (<i>p</i> < 0.0001, logrank test). Female CD-1 mice were injected intraperitoneally with 2.5 × 10⁷ CFU of GAS and lethality was monitored. Four ITP and four PTP strains were each used to infect 20 mice. Survival curves were generated by pooling data from mice infected with GAS strains of the same transcriptome profile.</p><p>(B) PTP GAS produce significantly larger lesion volumes than ITP GAS in a mouse soft-tissue infection model (<i>p</i> < 0.01, mixed-model repeated-measures analysis). Female Crl:SKH1-hrBR mice were injected subcutaneously with 1 × 10⁷ CFU of GAS and monitored for skin lesion formation. Shown are the average lesion volumes (± standard error of the mean) of mice pooled together based on the transcriptome profile of the infecting strain. Fifteen mice were infected per GAS strain, with four ITP and four PTP strains being used.</p></div