Evidence for novel polycyclic aromatic hydrocarbon degradation pathways in culturable marine isolates

IMPORTANCE

Polycyclic aromatic hydrocarbon (PAH) pollution is widespread throughout marine environments and significantly affects native flora and fauna. Investigating microbes responsible for degrading PAHs in these environments provides a greater understanding of natural attenuation in these systems. In addition, the use of culture-based approaches to inform bioinformatic and omics-based approaches is useful in identifying novel mechanisms of PAH degradation that elude genetic biomarker-based investigations. Furthermore, culture-based approaches allow for the study of PAH co-metabolism, which increasingly appears to be a prominent mechanism for PAH degradation in marine microbes.

Quorum Sensing and Antimicrobial Production Orchestrate Biofilm Dynamics in Multispecies Bacterial Communities

Microbial interactions are often mediated by diffusible small molecules, including secondary metabolites, that play roles in cell-to-cell signaling and inhibition of competitors. Biofilms are often "hot spots" for high concentrations of bacteria and their secondary metabolites, which make them ideal systems for the study of small-molecule contributions to microbial interactions. Here, we use a five-member synthetic community consisting of Roseobacteraceae representatives to investigate the role of secondary metabolites on microbial biofilm dynamics. One synthetic community member, Rhodobacterales strain Y4I, possesses two acylated homoserine lactone (AHL)-based cell-to-cell signaling systems (pgaRI and phaRI) as well as a nonribosomal peptide synthase gene (igi) cluster that encodes the antimicrobial indigoidine. Through serial substitution of Y4I with mutants deficient in single signaling molecule pathways, the contribution of these small-molecule systems could be assessed. As secondary metabolite production is dependent upon central metabolites, the influence of growth substrate (i.e., complex medium versus defined medium with a single carbon substrate) on these dynamics was also considered. Depending on the Y4I mutant genotype included, community dynamics ranged from competitive to cooperative. The observed interactions were mostly competitive in nature. However, the community harboring a Y4I variant that was both impaired in quorum sensing (QS) pathways and unable to produce indigoidine (pgaR variant) shifted toward more cooperative interactions over time. These cooperative interactions were enhanced in the defined growth medium. The results presented provide a framework for deciphering complex, small-molecule-mediated interactions that have broad application to microbial biology. IMPORTANCE Microbial biofilms play critical roles in marine ecosystems and are hot spots for microbial interactions that play a role in the development and function of these communities. Roseobacteraceae are an abundant and active family of marine heterotrophic bacteria forming close associations with phytoplankton and carrying out key transformations in biogeochemical cycles. Group members are aggressive primary colonizers of surfaces, where they set the stage for the development of multispecies biofilm communities. Few studies have examined the impact of secondary metabolites, such as cell-to-cell signaling and antimicrobial production, on marine microbial biofilm community structure. Here, we assessed the impact of secondary metabolites on microbial interactions using a synthetic, five-member Roseobacteraceae community by measuring species composition and biomass production during biofilm growth. We present evidence that secondary metabolites influence social behaviors within these multispecies microbial biofilms, thereby improving understanding of bacterial secondary metabolite production influence on social behaviors within marine microbial biofilm communities.

Odontodysplasia. Report of three cases with vascular nevi overlying the adjacent skin of the face

Three cases of odontodysplasia are described, and the literature is reviewed with reference to proposed etiologic mechanisms underlying the pathogenesis of the disorder. The distribution of affected teeth in all four quadrants of one patient is offered as evidence against a somatic mutation as an etiologic mechanism. As infants all three patients had vascular nevi in the facial skin overlying the area where defective teeth developed. Three cases from the literature involved similar vascular lesions. Hypoplastic teeth radiographically similar to odontodysplastic teeth occur in the linear sebaceous nevus syndrome. These findings strongly suggest that local vascular defects are involved in the pathogenesis of odontodysplasia.

The effect of moderate exercise on blood metabolites in patients with hypopituitarism

1. Six patients with panhypopituitarism and eight controls were studied before, during and after 30 min of moderate, steady exercise on a bicycle ergometer. Venous blood samples were taken for estimation of growth hormone, pyruvate, lactate, glucose, FFA, glycerol and ketone bodies.

2. Exercise caused a rise in serum growth hormone levels in control subjects and these fell to pre-exercise levels within 90 min. There was no change in the levels in the patients. The patients showed changes in blood metabolites resembling those of the controls. FFA levels were considerably elevated and post-exercise ketosis developed, these changes being more marked in the patients.

3. The differences in FFA and ketone bodies between patients and controls may be due to the lower levels of fitness in the patients. A further explanation may be that growth hormone depresses FFA levels after initial mobilization during exercise in normal subjects, but no such action can occur in patients with hypopituitarism.

4. It is concluded that growth hormone does not necessarily have a major role in fat mobilization or in the production of post-exercise ketosis. Thus, the lower levels of ketosis observed in athletes are not due to their lower levels of growth hormone.