Carrion beetles (Coleoptera: Silphidae) consist of two subfamilies in North America. Members of the Silphinae arrive at carcasses during the mid-stage of decay and their larvae feed on developing maggots, while members of the Nicrophorinae bury and tend carcasses upon which their developing larvae feed. The Nicrophorinae maintain the condition of the carcass by applying oral and anal secretions that reduce carcass decay apparently through bacterial inhibition, although quantification has not been made. We hypothesized that enzymes in the oral and anal secretions of the subfamily Nicrophorinae would inhibit bacterial growth, while secretions from the subfamily Silphinae would not. The secretions were assayed for inhibitory effects with a Microtox Analyzer that monitors the decrease in bioluminescence from the bacterium Vibrio fischerii. We found a significant difference of bioluminescence in the control compared to secretions of 8 out of 10 tested Nicrophorinae (with oral secretions being most active), while only anal secretions from Necrodes surinimensis of the Siphinae significantly reduced bacterial survival. These data follow the known phylogenic relationship in which Necrodes is the closest genus to the Nicrophorinae. The two species of Nicrophorinae, which did not show significant reductions in bacterial growth, differ ecologically from the others. Thus, the presence of antimicrobial compounds in most Nicrophorinae secretions, but not in most other Silphinae, represents an adaptation to preserve the buried carcass.

Carrion beetles of the subfamily Nicrophorinae search and bury a carcass that they utilize for reproduction. After burial, the carcass is coated with oral secretions that delay its decomposition. Previously, oral secretions of Nicrophorus marginatus were found to show antimicrobial activity, whereas secretion of N. carolinus lacked significant activity. Here, we tested the effects of temperature, sex of the beetle, and food type on the antimicrobial properties of oral secretions of both species. Unlike previous findings, we found that oral secretions of N. carolinus had antimicrobial activity. Temperature had significant effects on the amount of secretion protein. When protein concentrations were standardized to 1 micro/ml, N. marginatus secretions had higher antimicrobial activity at cooler temperatures, while N. carolinus had higher activity at warmer ones. The sex of the beetle did not affect antimicrobial activity for either species. Beetles of both species that were fed whole rats contained more protein in their oral secretions than beetles fed with equally sized pieces of raw ground beef. After standardizing the resulting protein concentrations to 1 microg/ml, antimicrobial activity of oral secretion increased for N. carolinus after rat feeding, but not for N. marginatus. Our results highlight key ecological differences between these closely related species. In addition, they demonstrate the importance of experiments being conducted under varying environmental conditions when evaluating species for potential antimicrobial compounds.

Reactivation of UV-C-inactivated Pseudomonas aeruginosa bacteriophages D3C3, F116, G101, and UNL-1 was quantified in host cells infected during the exponential phase, during the stationary phase, and after starvation (1 day, 1 and 5 weeks) under conditions designed to detect dark repair and photoreactivation. Our experiments revealed that while the photoreactivation capacity of stationary-phase or starved cells remained about the same as that of exponential-phase cells, in some cases their capacity to support dark repair of UV-inactivated bacteriophages increased over 10-fold. This enhanced reactivation capacity was correlated with the ca. 30-fold-greater UV-C resistance of P. aeruginosa host cells that were in the stationary phase or exposed to starvation conditions prior to irradiation. The dark repair capacity of P. aeruginosa cells that were infected while they were starved for prolonged periods depended on the bacteriophage examined. For bacteriophage D3C3 this dark repair capacity declined with prolonged starvation, while for bacteriophage G101 the dark repair capacity continued to increase when cells were starved for 24 h or 1 week prior to infection. For G101, the reactivation potentials were 16-, 18-, 10-, and 3-fold at starvation intervals of 1 day, 1 week, 5 weeks, and 1.5 years, respectively. Exclusive use of exponential-phase cells to quantify bacteriophage reactivation should detect only a fraction of the true phage reactivation potential.Numerous studies have demonstrated that significant numbers of viruses exist throughout the biosphere (3, 23, 29). For instance, bacteriophages are estimated to account for ca. 1% of the dissolved organic carbon in the open ocean (3). This relative abundance raises the question whether these bacteriophages merely persist or are functional and infective or whether, as found for the cyanophages (15), both possibilities are correct. We are interested in suitable methods for studying phage dynamics in aquatic ecosystems, i.e., suitable methods for monitoring the numbers and types of phages present over time. In this regard, there should be a dynamic equilibrium between the production of new phages following infection and the disappearance of phages, usually from one of three primary causes (21, 28): (i) consumption by grazing protozoans; (ii) attachment to labile colloids; and (iii) inactivation by UV radiation. Accurate estimates of the infective phage potential of a given sample or environment must take into consideration both the extent of the solar UV damage to the phage population and the availability of suitable bacterial hosts which could repair the damaged phage DNA.Previously, we addressed the question of phage reproductive potential in changing ecosystems by looking at the prevalence of broad-host-range bacteriophages able to infect multiple bacterial species, including Sphaerotilus natans, Escherichia coli, and Pseudomonas aeruginosa (11). It is probable that any UVdamaged broad-host-range bacteriophages are capable of undergoing reactivation in several dif...

Flies are known to be mechanical vectors of bacterial, viral, and parasitic diseases. Although flies are known to transmit disease, the effects of cleaning behavior have not been well studied. This study quantified the cleaning effectiveness and behavior of three fly species: Sarcophaga bullata, Musca domestica L., and Drosophila virilis. Flies were transferred to plates of Escherichia coli or Pseudomonas aeruginosa and allowed to walk on the bacteria for a total of 5 min. After the flies were contaminated, they were either immediately collected to quantify bacteria or were placed onto sterile plates to clean for 5 or 10 min. After cleaning, flies were placed into tubes with 1 ml of sterile 0.85% saline and were gently shaken for 1 min to remove bacteria. A serial dilution was made and 50-µl spot titers were plated. Cleaning behavior was also monitored and scored for a period of 5 min. Results demonstrate a bacterial reduction for both bacteria on all three fly species. Sarcophaga bullata and D. virilis both showed a significant reduction of both bacteria within 10 min, whereas M. domestica only showed a significant reduction in P. aeruginosa. Cleaning behavior increased significantly in flies that were exposed to bacteria compared to flies that were not exposed to bacteria. This study is important, as it demonstrates that fly cleaning could affect mechanical transmission of disease, and additional studies should look at flies' abilities to remove other types of microorganisms.

Both the moderately halophilic bacterium, Halomonas elongata, and the extremely halophilic archaea, Halobacterium salinarum, can be found in hypersaline environments (e.g., salterns). On complex media, H. elongata grows over a salt range of 0.05-5.2 M, whereas, H. salinarum multiplies over a salt range of 2.5-5.2 M. The purpose of this study was to illustrate the effect that solar (UV-A and UV-B) and germicidal radiation (UV-C) had on the growth patterns of these bacteria at varied salt concentrations. Halomonas elongata grown on a complex medium at 0.05, 1.37, and 4.3 M NaCl was found to be more sensitive to UV-A and UV-B radiation, as the salt concentration of the medium increased. Halobacterium salinarum grown on a complex medium at 3.0 and 4.3 M NaCl did not show a significant drop in viability after 39.3 kJ.m-2 of UV-A and UV-B exposure. When exposed to UV-C, H. elongata exhibited substantially more sensitivity than H. salinarum. In H. elongata, differential sensitivity to UV-C was observed. At 0.05 M NaCl, H. elongata was less sensitive to UV-C than at 1.37 and 4.3 M NaCl. Both bacteria showed some photoreactivation when incubated under visible light following both UV-A, UV-B, and UV-C exposure. Mutagenesis following UV-C exposure was demonstrated by both organisms.