Biology subjects

Townsend, K. A.

Publications and source records attributed to Townsend, K. A..

6 recordsLinked to original sources

bioRxiv2025

Valuing conservation and natural wealth: The blue economy of manta ray watching in the Maldives

Amid declining manta ray populations globally, the well-established and growing manta ray tourism industries generate substantial economic benefits and aid protective legislation for these threatened elasmobranchs. As flagship species, manta rays are a drawcard for marine wildlife tourism and a gateway for engaging the public and communities in conservation. Healthy marine ecosystems are the key drivers of employment and economic sustainability for island nations such as the Maldives. However, there are many stakeholders competing for these shared resources, which can result in environmental degradation. Economic evaluations are a powerful tool for justifying the conservation efforts of threatened species and natural areas, especially in light of competing stakeholders. Using tour operator surveys (n=106) and data mining, this study provides an updated assessment of manta ray watching tourism in the Maldives, and represents the first national evaluation of its total economic and socio-economic benefits. In 2021, manta ray tourism in the Maldives generated an estimated US$227.3 million, including US$39 million on manta ray focused diving and snorkelling excursions, and US$188.3 million in related tourist expenditure. This represented 4.8% of the national Gross Domestic Product. This industry appears to have grown around 380% since 2008 (US$8.1 million) and manta ray watching is now offered by 80% of tourism operators nation-wide. Our findings revealed that manta rays hold intrinsic value and cultural significance within local communities. Acknowledging this, the flow-on benefits to the community extend beyond this industry, reaching local businesses, employed staff, and the government with the total economic benefits of the manta ray tourism industry were estimated at over US$311 million per year. Such value highlights the significance of manta rays for this nation and the need for effective management centred on manta ray conservation to safeguard future prosperity and mitigate the potential impact of tourism on manta ray populations.

ecology↗

bioRxiv2024

Characterization of natural product inhibitors of quorum sensing in Pseudomonas aeruginosa reveals competitive inhibition of RhlR by ortho-vanillin

Quorum sensing (QS) is a cell-cell signaling system that enables bacteria to coordinate population density-dependent changes in behavior. This chemical communication pathway is mediated by diffusible N-acyl L-homoserine lactone signals and cytoplasmic signal-responsive LuxR-type receptors in Gram-negative bacteria. As many common pathogenic bacteria use QS to regulate virulence, there is significant interest in disrupting QS as a potential therapeutic strategy. Prior studies have implicated the natural products salicylic acid, cinnamaldehyde and other related benzaldehyde derivatives as inhibitors of QS in the opportunistic pathogen Pseudomonas aeruginosa, yet we lack an understanding of the mechanisms by which these compounds function. Herein, we evaluate the activity of a set of benzaldehyde derivatives using heterologous reporters of the P. aeruginosa LasR and RhlR QS signal receptors. We find that most tested benzaldehyde derivatives can antagonize LasR or RhlR reporter activation at micromolar concentrations, although certain molecules also caused mild growth defects and nonspecific reporter antagonism. Notably, several compounds showed promising RhlR or LasR specific inhibitory activities over a range of concentrations below that causing toxicity. ortho-Vanillin, a previously untested compound, was the most promising within this set. Competition experiments against the native ligands for LasR and RhlR revealed that ortho-vanillin can interact competitively with RhlR but not with LasR. Overall, these studies expand our understanding of benzaldehyde activities in the LasR and RhlR receptors and reveal potentially promising effects of ortho-vanillin as a small molecule QS modulator against RhlR. IMPORTANCE Quorum sensing (QS) regulates many aspects of pathogenesis in bacteria and has attracted interest as a target for anti-virulence therapies. As QS is regulated by low molecular weight chemical signals, the development of chemical strategies that can interfere with this cell-cell communication pathway has seen considerable scrutiny over the past 25 years. Much of this research has focused on common human pathogens, including the LasR and RhlR QS receptors in Pseudomonas aeruginosa. Potent and selective chemical agents capable of blocking the activity of these receptors remain relatively scarce, however. Natural products have provided a bounty of chemical scaffolds with anti-QS activities, but their molecular mechanisms are poorly characterized. The current study serves to fill this void by examining the activity of an important and wide-spread class of natural product QS modulators, benzaldehydes and related derivatives, in LasR and RhlR. We demonstrate that ortho-vanillin can act as a competitive inhibitor of RhlR, a receptor that has emerged and may supplant LasR in certain settings as a target for QS control in P. aeruginosa. The results and insights provided herein will advance the design of chemical tools to study QS with improved activities and selectivities.

microbiology↗

bioRxiv2023

Tobramycin adaptation alters the antibiotic susceptibility of Pseudomonas aeruginosa quorum sensing-null mutants

The opportunistic bacterium Pseudomonas aeruginosa uses the LasR-I quorum sensing system to increase resistance to the aminoglycoside antibiotic tobramycin. Paradoxically, lasR-null mutants are commonly isolated from chronic human infections treated with tobramycin, suggesting there may be a mechanism allowing the lasR-null mutants to persist under tobramycin selection. We hypothesized that the effects of inactivating lasR on tobramycin resistance might be dependent on the presence or absence of other gene mutations in that strain, a phenomenon known as epistasis. To test this hypothesis, we inactivated lasR in several highly tobramycin-resistant isolates from long-term evolution experiments. We show that the effects of {Delta}lasR on tobramycin resistance are strain dependent, which is due to a single mutation in the fusA1 gene encoding the translation elongation factor EF-G1A (G61A nucleotide substitution). The fusA1 G61A mutation confers a strong selective advantage to {Delta}lasR mutants under tobramycin treatment. The effects of fusA1 G61A on {Delta}lasR-dependent tobramycin resistance are dependent on the MexXY efflux pump and the MexXY regulator ArmZ. The fusA1 mutation also modulates {Delta}lasR mutant resistance to two other antibiotics, ciprofloxacin and ceftazidime. Our results provide a possible explanation for the emergence of lasR-null mutants in clinical isolates and illustrate the importance of epistatic gene interactions in the evolution of quorum sensing.

microbiology↗

bioRxiv2019

The geographic distribution of reef and oceanic manta rays in the south-east Indian and south-west Pacific Oceans

The reef manta ray, Mobula alfredi, occurs in tropical and warm temperate coastal waters, and around islands and reefs in the Pacific and Indian Oceans. Published records that relate to the distribution of M. alfredi in the south-east Indian and south-west Pacific Oceans are largely restricted to locations where there is a focus on manta ray ecotourism, with little information from elsewhere. Even less is known about the circumglobally distributed oceanic manta ray, Mobula birostris, for which there are few published sighting records. We collated n = 11,703 sighting records from Australian waters and offshore territories for M. alfredi sourced from scientific image databases (n = 10,715), aerial surveys (n = 375) and online reports (n = 613). From collated records, we confirm that the species shows an uninterrupted distribution within Australian coastal waters north of 26{degrees}S on the west coast to 31{degrees}S on the east coast, with a southernmost record at 34{degrees}S. Confirmed locations for M. birostris encompass a latitudinal range of 10-40{degrees}S. Records from more southerly locations relate to warm-water events. Sightings of M. birostris were rare, but were confirmed at several geographically separate locations, probably reflecting its preference for offshore waters. The study clarifies the occurrence and range of each species within coastal waters of the south-east Indian and south-west Pacific Oceans, and highlights regions in northern Australia that are of specific interest for future research into possible movements of individuals between international marine jurisdictions.

ecology↗

bioRxiv2018

The ecological cocktail party: Measuring brain activity during an auditory oddball task with background noise

Most experiments using EEG recordings take place in highly isolated and restricted environments, limiting their applicability to real-life scenarios. New technologies for mobile EEG are changing this by allowing EEG recording to take place outside of the laboratory. However, before results from experiments performed outside the laboratory can be fully understood, the effects of ecological stimuli on brain activity during cognitive tasks must be examined. In this experiment, participants performed an auditory oddball task while also listening to concurrent background noises of silence, white noise and outdoor ecological sounds, as well as a condition in which the tones themselves were at a low volume. We found a significantly increased N1 and decreased P2 when participants performed the task with outdoor sounds and white noise in the background, with the largest differences in the outdoor sound condition. This modulation in the N1 and P2 replicates what we have previously found outside while people ride bicycles (Scanlon et al., 2017). No behavioural differences were found in response to the target tones. We interpret these modulations in early ERPs as indicative of sensory filtering of background sounds, and that ecologically valid sounds require more filtering than synthetic sounds. Our results reveal that much of what we understand about the brain will need to be updated as we step outside the lab.

neuroscience↗

bioRxiv2017

Taking off the training wheels: Measuring auditory P3 during outdoor cycling using an active wet EEG system

Mobile EEG allows the investigation of brain activity in increasingly complex environments. In this study, EEG equipment was adapted for use and transportation in a backpack while cycling. Participants performed an auditory oddball task while cycling outside and sitting in an isolated chamber inside the lab. Cycling increased EEG noise and marginally diminished alpha amplitude. However, this increased noise did not influence the ability to measure reliable event related potentials (ERP). The P3 was similar in topography, and morphology when outside on the bike, with a lower amplitude in the outside cycling condition. There was only a minor decrease in the statistical power to measure reliable ERP effects. Unexpectedly, when biking outside significantly decreased P2 and increased N1 amplitude were observed when evoked by both standards and targets compared with sitting in the lab. This may be due to attentional processes filtering the overlapping sounds between the tones used and similar environmental frequencies. This study established methods for mobile recording of ERP signals. Future directions include investigating auditory P2 filtering inside the laboratory.\n\nHighlightsO_LIA backpack containing all the equipment necessary to record ERP and EEG was worn by participants as they rode a bicycle outside along a street\nC_LIO_LIEEG and ERP data from an auditory oddball task is compared with data acquired within-subject inside the lab\nC_LIO_LIReliable MMN/N2b and P3 responses were measured during bicycle riding outside equal in magnitude to those obtained inside the lab\nC_LIO_LIA surprising decrease in the P2 component of the ERP evoked by targets and standards was observed when doing the task outside on a bicycle, which we attribute to increased auditory filtering\nC_LI

neuroscience↗