L. L. Blackall

Induction of larval metamorphosis of the coral Acropora millepora by tetrabromopyrrole isolated from a Pseudoalteromonas bacterium.

The induction of larval attachment and metamorphosis of benthic marine invertebrates is widely considered to rely on habitat specific cues. While microbial biofilms on marine hard substrates have received considerable attention as specific signals for a wide and phylogenetically diverse array of marine invertebrates, the presumed chemical settlement signals produced by the bacteria have to date not been characterized. Here we isolated and fully characterized the first chemical signal from bacteria that induced larval metamorphosis of acroporid coral larvae (Acropora millepora). The metamorphic cue was identified as tetrabromopyrrole (TBP) in four bacterial Pseudoalteromonas strains among a culture library of 225 isolates obtained from the crustose coralline algae Neogoniolithon fosliei and Hydrolithon onkodes. Coral planulae transformed into fully developed polyps within 6 h, but only a small proportion of these polyps attached to the substratum. The biofilm cell density of the four bacterial strains had no influence on the ratio of attached vs. non-attached polyps. Larval bioassays with ethanolic extracts of the bacterial isolates, as well as synthetic TBP resulted in consistent responses of coral planulae to various doses of TBP. The lowest bacterial density of one of the Pseudoalteromonas strains which induced metamorphosis was 7,000 cells mm−2 in laboratory assays, which is on the order of 0.1 –1% of the total numbers of bacteria typically found on such surfaces. These results, in which an actual cue from bacteria has been characterized for the first time, contribute significantly towards understanding the complex process of acroporid coral larval settlement mediated through epibiotic microbial biofilms on crustose coralline algae.

Phylogenetic analysis of Porphyromonas species isolated from the oral cavity of Australian marsupials

Porphyromonas species are frequently isolated from the oral cavity and are associated with periodontal disease in both animals and humans. Black, pigmented Porphyromonas spp. isolated from the gingival margins of selected wild and captive Australian marsupials with varying degrees of periodontal disease (brushtail possums, koalas and macropods) were compared phylogenetically to Porphyromonas strains from non-marsupials (bear, wolf, coyote, cats and dogs) and Porphyromonas gingivalis strains from humans using 16S rRNA gene sequence analysis. The results of the phylogenetic analysis identified three distinct groups of strains. A monophyletic P. gingivalis group (Group 1) contained only strains isolated from humans and a Porphyromonas gulae group (Group 2) was divided into three distinct subclades, each containing both marsupial and non-marsupial strains. Group 3, which contained only marsupial strains, including all six strains isolated from captive koalas, was genetically distinct from P. gulae and may constitute a new Porphyromonas species.

Using Bacterial Extract along with Differential Gene Expression in Acropora millepora Larvae to Decouple the Processes of Attachment and Metamorphosis

Biofilms of the bacterium Pseudoalteromonas induce metamorphosis of acroporid coral larvae. The bacterial metabolite tetrabromopyrrole (TBP), isolated from an extract of Pseudoalteromonas sp. associated with the crustose coralline alga (CCA) Neogoniolithon fosliei, induced coral larval metamorphosis (100%) with little or no attachment (0–2%). To better understand the molecular events and mechanisms underpinning the induction of Acropora millepora larval metamorphosis, including cell proliferation, apoptosis, differentiation, migration, adhesion and biomineralisation, two novel coral gene expression assays were implemented. These involved the use of reverse-transcriptase quantitative PCR (RT-qPCR) and employed 47 genes of interest (GOI), selected based on putative roles in the processes of settlement and metamorphosis. Substantial differences in transcriptomic responses of GOI were detected following incubation of A. millepora larvae with a threshold concentration and 10-fold elevated concentration of TBP-containing extracts of Pseudoalteromonas sp. The notable and relatively abrupt changes of the larval body structure during metamorphosis correlated, at the molecular level, with significant differences (p<0.05) in gene expression profiles of 24 GOI, 12 hours post exposure. Fourteen of those GOI also presented differences in expression (p<0.05) following exposure to the threshold concentration of bacterial TBP-containing extract. The specificity of the bacterial TBP-containing extract to induce the metamorphic stage in A. millepora larvae without attachment, using a robust, low cost, accurate, ecologically relevant and highly reproducible RT-qPCR assay, allowed partially decoupling of the transcriptomic processes of attachment and metamorphosis. The bacterial TBP-containing extract provided a unique opportunity to monitor the regulation of genes exclusively involved in the process of metamorphosis, contrasting previous gene expression studies that utilized cues, such as crustose coralline algae, biofilms or with GLW-amide neuropeptides that stimulate the entire onset of larval metamorphosis and attachment.

Further limitations of phylogenetic group-specific probes used for detection of bacteria in environmental samples

Further limitations of phylogenetic group-specific probes used for detection of bacteria in environmental samples

16S rRNA gene based PCR detection of Bacteroides forsythus in pooled subgingival plaque

Corticosteroids are widely used today in the medical treatment of many chronic illnesss. It has hem well docunnented that corticosteroids affect hone metabolism and this rnaie concemas as so the effect of coeticosteroid treatent on orthodontic tooth movemiernt. The aimn of this study was to determine Ithe effect of an elevated physiologic level of corticosteroid on bone rmnodeling daring orthodontic movement. Twelve 9-weak old adult male Wisuar rate were divided into two groups- a corticosteroid treated group (n=6) and a control group (n=6). The corticosteroid treate group was admiinistered ltngik of oral prednisolone daily for a 12-day induction period, while the control group received the equivalent volumes of saline for the tame liTme period. Following thin induction period, an orthodontiC appiance was ligated between the maxillary first left molar and two nmaxillary central incisors such thata menia force of 30g wasW T R W generated. The molar on the right skide was used an the son-appliance control. All sanimals were sacrificedIT WDR after 12 days of appliance wear. The magnitude of tooth mnovement was recoorded. Maxillse were fixed, demineralised and processed to paraffin. Sagittal sections of the first molar were staned with harmatoxylin and cosin and for turtrate-resistant acid phosphatase (TRAP) activity. For thin dose of prednisolone, there are no significant differences (p<0.05) in the magnitude of tooth imovement between the treated and control groups. Steroid treaed rats displayed lens root resorption along the length of the root on the coespressive side as well as fewer TRAP positive cells widthin the PDL space of the comspressive side, conmpaed to the non-sterid control (p.Z0.05). There was more TRAP activity recorded along the tension-side alveolar bone surface (cervcal third) in the steroid treated rats comspared to the son steroid controls (pr0O05). The rate of orthodontic movements was unaffected by lessgIsa of orednisolone. The easth of root renemtion alon th menial comprenson side and the TRAP activity at the comoression side PDL were both reduced. suagenlise that a susorenion of clastic activity had taken place. This study was supported by an ADRF grat.