Acute Exposure to Two Biocides Causes Morphological and Molecular Changes in the Gill Ciliary Epithelium of the Invasive Golden Mussel Limnoperna fortunei (Dunker, 1857).

Limnoperna fortunei, the golden mussel, is a bivalve mollusk considered an invader in South America. This species is responsible for ecological and economic damages due to its voluminous fouling capability. Chemical biocides such as MXD-100™ and sodium dichloroisocyanurate (NaDCC) are often used to control L. fortunei infestations in hydraulic systems. Thus, we proposed to investigate the effects of different periods (24, 48 and 72 h) of exposure to MXD-100™ (0.56 mg L-1) and NaDCC (1.5 mg L-1) on the gills of L. fortunei through morphological and molecular analyses. NaDCC promoted progressive morphological changes during the analyzed periods and only an upregulation of SOD and HSP70 expression during the first 24 h of exposure. MXD-100™ led to severe morphological changes from the first period of exposure, in addition to an upregulation of SOD, CAT, HSP70 and CYP expression during the first 24 h. In contrast, MXD-100™ led to a downregulation of CAT transcription between 24 and 48 h. In static conditions, NaDCC causes lethal damage after 72 h of exposure, and that exposure needs to be continuous to achieve the control of the species. Meanwhile, the MXD-100™ treatment presented several effects during the first 24 h, showing acute toxicity in a shorter period of time.

Linking microbial slime community structure with abiotic factors and antifouling strategy in hydroelectric cooling systems.

Microfouling can have significant economic impacts for hydroelectric power plants. However, knowledge concerning the composition and metabolism of microbial biofilm in cooling systems remains scarce. We examined the metagenome present in a cooling system, comprising a filter (F) and heat exchanger (HE), in the Nova Ponte hydroelectric power plant in Brazil, to identify bacteria and pathways that could be targeted to monitor and control biofilm formation. Our data revealed that the microfouling sample from heat exchanger 1 (HEM1), with porous consistency, presented enriched bacterial members not frequently described as biofilm formers in cooling systems, besides it has been shown to be an autoinducer repression pathway. Furthermore, the microfouling sample from heat exchanger 2 (HEM2), with gelatinous consistency, seemed to be an established biofilm, containing enriched bacterial groups such as Desulfotomaculum and Crenothrix and autoinducers, with biotechnological relevance in industrial biofilms. The results demonstrate that biofilm composition will vary depending on different abiotic conditions and the antifouling strategy used, including type of compound, concentration, and frequency of use. Therefore, all these variables must be evaluated when a power plant is affected by microbial slime in the cooling system. Our findings could help to define strategies for efficient and ecofriendly measures to contain microfouling in power plants.

Microbial composition of a hydropower cooling water system reveals thermophilic bacteria with a possible role in primary biofilm formation.

Microfouling, ie biofilm formation on surfaces, can have an economic impact and requires costly maintenance in water-powered energy generation systems. In this study, the microbiota of a cooling system (filter and heat exchanger) in the Irapé hydroelectric power plant in Brazil was examined. The goal was to identify bacteria that could be targeted to more efficiently reduce biofilm formation. Two sampling campaigns were made corresponding to two well-defined seasons of the Brazilian Cerrado biome: the dry (campaign 1) and the wet (campaign 2). Microfouling communities varied considerably over time in samples obtained at different times after the last clearance of the heat exchanger. The thermophilic bacteria Meiothermus, Thermomonas and Symbiobacterium were exclusive and abundant in the microfouling of the heat exchanger in campaign 2, while methanotrophs and iron-reducing bacteria were abundant only in filter sediments. These findings could help to guide strategies for ecofriendly measures to reduce biofilm fouling in hydroelectric power plants, minimizing environmental and economic losses.

Porcine stomachs with and without gastric ulcer differ in Lactobacillus load and strain characteristics.

Although Lactobacillus species are recognized as normal inhabitants of porcine gastric mucosa, the association of these bacteria with health status or gastric ulcer disease has never been considered. We investigated the bacterial load of Lactobacillus isolated from the antrum, corpus, and pars esophagea of stomachs with (n = 13) and without (n = 10) ulcer of the pars esophagea of slaughtered pigs. We also evaluated in vitro antagonistic properties against typical pathogens of strains isolated from stomachs without ulcer. To quantify Lactobacillus, gastric mucosa samples obtained with 5 mm biopsy punches were smeared on MRS agar and colonies were counted after 48 h of incubation under anaerobic conditions. The score of Lactobacillus was significantly greater in the antrum and corpus of stomachs without ulcer (P < 0.001 for both) when compared with stomachs with ulcer. Fingerprint profiles, obtained by repetitive sequence-based PCR using (GTG)5 primers, showed that the isolates were highly diverse. The reduction of Lactobacillus load in porcine stomachs may be a contributing factor for gastric ulcer. Strains isolated from healthy stomachs, which showed a wide spectrum of antagonistic activity against pathogens, may be viewed as an untapped source of bacteria with potential beneficial properties that deserve to be further investigated.

Antibiotic resistance profile and occurrence of AmpC between Pseudomonas aeruginosa isolated from a domestic full-scale WWTP in southeast Brazil.

Wastewater treatment plants (WWTPs) represent an important reservoir of antibiotic resistance determinants. Although many studies have been conducted to evaluate resistance profiles in Enterobacteriaceae isolates from this setting, the dynamics of this phenomenon are poorly known to the bacterium Pseudomonas aeruginosa. Here we aimed to evaluate the resistance profiles and the production of AmpC ß-lactamase in P. aeruginosa isolates from a domestic full-scale WWTP. Samples of the raw sewage and effluent were collected and the bacterium P. aeruginosa was isolated on cetrimide agar. Susceptibility to ß-lactams, fluoroquinolones and aminoglycosides was evaluated by the disc diffusion method, and the presence of AmpC ß-lactamase was investigated phenotypically and by molecular method. We recovered 27 isolates of P. aeruginosa. Of these, 81.5% were susceptible to all antimicrobials tested. However, a considerable rate of resistance to carbapenems (11%) was found among the isolates. Twenty-two isolates were positive in the phenotypic test for inducible AmpC ß-lactamase but the blaampc gene was only identified in four isolates, suggesting the presence of other independent resistance mechanisms besides this ß-lactamase. In summary, we have shown that P. aeruginosa isolates from a domestic WWTP represents a potential reservoir of blaampC genes and other resistance determinants, including those that result in low susceptibility to carbapenems and aminoglycosides.