Para-Aminobenzoic Acid, Calcium, and c-di-GMP Induce Formation of Cohesive, Syp-Polysaccharide-Dependent Biofilms in Vibrio fischeri

The marine bacterium Vibrio fischeri efficiently colonizes its symbiotic squid host, Euprymna scolopes, by producing a transient biofilm dependent on the symbiosis polysaccharide (SYP). In vitro, however, wild-type strain ES114 fails to form SYP-dependent biofilms. Instead, genetically engineered strains, such as those lacking the negative regulator BinK, have been developed to study this phenomenon. Historically, V. fischeri has been grown using LBS, a complex medium containing tryptone and yeast extract; supplementation with calcium is required to induce biofilm formation by a binK mutant. Here, through our discovery that yeast extract inhibits biofilm formation, we uncover signals and underlying mechanisms that control V. fischeri biofilm formation. In contrast to its inability to form a biofilm on unsupplemented LBS, a binK mutant formed cohesive, SYP-dependent colony biofilms on tTBS, modified LBS that lacks yeast extract. Moreover, wild-type strain ES114 became proficient to form cohesive, SYP-dependent biofilms when grown in tTBS supplemented with both calcium and the vitamin para-aminobenzoic acid (pABA); neither molecule alone was sufficient, indicating that this phenotype relies on coordinating two cues. pABA/calcium supplementation also inhibited bacterial motility. Consistent with these phenotypes, cells grown in tTBS with pABA/calcium were enriched in transcripts for biofilm-related genes and predicted diguanylate cyclases, which produce the second messenger cyclic-di-GMP (c-di-GMP). They also exhibited elevated levels of c-di-GMP, which was required for the observed phenotypes, as phosphodiesterase overproduction abrogated biofilm formation and partially rescued motility. This work thus provides insight into conditions, signals, and processes that promote biofilm formation by V. fischeri. IMPORTANCE Bacteria integrate environmental signals to regulate gene expression and protein production to adapt to their surroundings. One such behavioral adaptation is the formation of a biofilm, which can promote adherence and colonization and provide protection against antimicrobials. Identifying signals that trigger biofilm formation and the underlying mechanism(s) of action remain important and challenging areas of investigation. Here, we determined that yeast extract, commonly used for growth of bacteria in laboratory culture, inhibits biofilm formation by Vibrio fischeri, a model bacterium used for investigating host-relevant biofilm formation. Omitting yeast extract from the growth medium led to the identification of an unusual signal, the vitamin para-aminobenzoic acid (pABA), that when added together with calcium could induce biofilm formation. pABA increased the concentrations of the second messenger, c-di-GMP, which was necessary but not sufficient to induce biofilm formation. This work thus advances our understanding of signals and signal integration controlling bacterial biofilm formation

Reactivation of Coccidioidomycosis in a Mouse Model of Asymptomatic Controlled Disease

The majority of human coccidioidomycosis infections are asymptomatic or self-limited but may have sequestered spherules in highly structured granulomas. Under immunosuppression, reactivation of fungal growth can result in severe disease. B6D2F1 mice asymptomatically infected with C. posadasii strain 1038 were immunosuppressed with dexamethasone (DXM) in drinking water. Treated mice died 16–25 days later, while untreated mice survived (p < 0.001). Flow cytometry of lung granulomas on days 5, 10, 15, and 20 of DXM treatment showed immune cell populations decreased 0.5–1 log compared with untreated mice though neutrophils and CD19+IgD−IgM− cells rebounded by day 20. Histopathology demonstrated loss of granuloma structure by day 5 and increasing spherules through day 20. On day 20, T-cells were nearly absent and disorganized pyogranulomatous lesions included sheets of plasma cells and innumerable spherules. Mice given DXM for 14 days then stopped (DXM stop) survived 6 weeks (9/10). Lung fungal burdens were significantly lower (p = 0.0447) than mice that continued treatment (DXM cont) but higher than untreated mice. Histopathologically, DXM stop mice did not redevelop controlled granulomas by sacrifice, though T-cells were densely scattered throughout the lesions. This demonstrates a mouse model suitable for further study to understand the immunologic components responsible for maintenance control of coccidioidomycosis. © 2022 by the authors.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Tratamento homeopático da hepatotoxicose aguda induzida por tetracloreto de carbono em coelhos Homeopatic treatment of acute carbon tetrachloride induced hepatotoxicity in rabbits

Quinze (15) coelhos (Oryctolagus cuniculus) foram submetidos à intoxicação pelo tetracloreto de carbono na dosagem de 0,5 ml/kg de peso corporal, dose única, administrado por sonda gástrica. Foram realizadas as dosagens de alanina amino transferase (ALT), aspartato amino transferase (AST), fosfatase alcalina (FA) e gama glutamil transferase (GGT) antes e durante o experimento. Vinte e quatro (24) horas após a intoxicação, os coelhos foram divididos aleatoriamente em três grupos de 5 animais. Cada grupo recebeu um tratamento diferente durante 13 dias. O grupo I foi tratado com tetracloreto de carbono diluído na 30&ordf; centesimal hahnemanniana (30 CH), uma vez ao dia. O grupo II recebeu Phosphorus 30 CH, também uma vez ao dia. O grupo III desempenhou o papel de controle, recebendo diariamente uma dose de placebo, pelo mesmo período de tempo que os grupos anteriores. Os resultados das concentrações séricas de ALT, AST, GGT e FA foram submetidos à análise estatística. A variação da concentração de todas as enzimas foi significativa entre os dias, mas nem todas variaram significativamente entre os grupos considerados. O tetracloreto de carbono 30 CH foi capaz de acelerar a recuperação do quadro de hepatite tóxica aguda determinada pela redução dos níveis de ALT. O tratamento com Phosphorus 30 CH mostrou-se incapaz seja de reverter o quadro de hepatite tóxica, seja de acelerar a regeneração hepática.<br>Fithteen (15) New Zeland and Californian rabbits (Oryctolagus cuniculus) were submitted to intoxication with carbon tethracloride in a dose 0/0.5 ml/kg, once a day, administred by orogastric sonde. Enzimatic parameters: alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase and gamma-glutamyltransferase of those rabbits were tested before and during the experiment. After the intoxication, the rabbits were divided in three groups of five animals. Each group received differents treatments during 13 days. The animals in group I were treated with carbon tetrachloride 30 CH, once a day. The animals in group II were treated with Phosphorus 30 CH also once a day. The rabbits in group III served as a control receiving the same quantity of placebo with the same protocol of lhe others. The blood samples were obtained by cardiac puncture every 4 days. The seric concentrations of ALT, AST, GGT and FA were submited to estatistic avaliation. The variation of all enzimes tested was significant between the days, but not always between the groups. This study demonstrated thaf carbon tetrachloride 30 CH was efficient in acelerating the recuperation of normal levels of ALT, but the terapy with Phosphorus 30 CH was insufficient for reverting the hepatic intoxication

Pitiose em animais de produção no Pantanal Matogrossense

Realizou-se, em quatro propriedades rurais no Pantanal Matogrossense, em 2009 e 2010, um estudo clínico e epidemiológico da pitiose em bovinos e equinos. A enfermidade ocorreu predominantemente entre os meses de novembro e março, correspondendo ao período chuvoso na região. A incidência média anual foi de 0,22% e 12,5% em bovinos e equinos, respectivamente. Nos bovinos, a distribuição dos casos ocorreu no ápice das cheias e restringiu-se a novilhas de 6 a 18 meses de idade, nas quais as lesões cutâneas estiveram associadas com edemas perilesionais discretos e claudicações, mas curaram espontaneamente, em um período máximo de 90 dias. Nos equinos, a pitiose acometeu animais de ambos os sexos, de três a oito anos de idade e registrou-se um caso de reinfecção. A doença evoluiu com agravos no sítio lesional, com desenvolvimento de extenso tecido de granulação, kunkersem permeio à lesão, acentuada caquexia e mortes, as quais ocorreram entre três e sete meses após o início dos sinais. A mortalidade média foi 5,88% e a letalidade 45,45%. A confirmação do diagnóstico incluiu ELISA-teste, PCR, histopatologia (HE e Grocott) e isolamento de P. insidiosum. Na área endêmica estudada, a enfermidade não causou impacto econômico em bovinos, a despeito da evolução insatisfatória registrada na maioria dos equinos. Nesse estudo, a incidência de pitiose em equinos foi 57,23 vezes a observada em bovinos, com significância estatística. Apesar das mesmas condições ambientais, tal diferença foi provavelmente associada com susceptibilidade, comportamento e manejo das espécies nos campos alagados