Regulation of gene expression: Cryptic β-glucoside (bgl) operon of Escherichia coli as a paradigm

Bacteria have evolved various mechanisms to extract utilizable substrates from available resources and consequently acquire fitness advantage over competitors. One of the strategies is the exploitation of cryptic cellular functions encoded by genetic systems that are silent under laboratory conditions, such as the bgl (β-glucoside) operon of E. coli. The bgl operon of Escherichia coli, involved in the uptake and utilization of aromatic β-glucosides salicin and arbutin, is maintained in a silent state in the wild type organism by the presence of structural elements in the regulatory region. This operon can be activated by mutations that disrupt these negative elements. The fact that the silent bgl operon is retained without accumulating deleterious mutations seems paradoxical from an evolutionary view point. Although this operon appears to be silent, specific physiological conditions might be able to regulate its expression and/or the operon might be carrying out function(s) apart from the utilization of aromatic β-glucosides. This is consistent with the observations that the activated operon confers a Growth Advantage in Stationary Phase (GASP) phenotype to Bgl+ cells and exerts its regulation on at least twelve downstream target genes.

Consumo materno de dois compostos bioativos da semente da linhaça sobre parâmetros bioquímicos e hormonais das mães e proles durante a lactação / Maternal consumption of two bioactive compounds from flax seed on biochemical and hormonal parameters of mothers and offspring during lactation

Avaliamos o efeito do consumo materno de SDG (Diglicosídeo Secoisolariciresinol) e de óleo de Linhaça+SDG sobre parâmetros bioquímicos e hormonais das ratas e das proles machos e fêmeas na lactação. As ratas lactantes foram separadas em: controle (C), ração controle cuja proteína foi caseína; (SDG): ração C com 400mg de SDG/Kg de ração; OLSDG: ração C com 400mg de SDG/Kg de ração e 7% de óleo de linhaça. No 14º e 20º dias de lactação as ratas foram ordenadas e no 21º dia foram sacrificadas por punção cardíaca. Leite e soro foram coletados para avaliação bioquímica e hormonal. Hormônios foram quantificados por radioimunoensaio. As proles machos e fêmeas foram sacrificadas aos 14 e 21 dias de idade. Os animais foram eviscerados para análise da composição corporal. Monitoramos a ingestão alimentar e a massa corporal (MC) durante o período experimental. As ratas SDG apresentaram maior gordura corporal (GC; +39%), enquanto as OLSDG menor conteúdo mineral (-20%) e trigliceridemia (TG) (-39%). As ratas SDG e OLSDG apresetaram hiperprolactinemia (+389% e 153%, respectivamente) sem alteração na concentração de estradiol. No 14º dia de lactação, o leite das ratas OLSDG apresentou menores teores de lactose (-17%) e de proteínas (-20%) e o das ratas SDG apenas menor teor de proteína (-21%). A partir do 13º dia de lactação tanto os machos quanto as fêmeas OLSDG apresentaram menor MC (-14%, -16%, respectivamente). No 14º dia de lactação os machos SDG e OLSDG apresentaram menor gordura corporal (-24%, -55%, respectivamente) e a prole SDG maior massa de gordura visceral (+39%). Os machos SDG apresentaram maiores concentrações de TG (+105%) e hipoprolactinemia (-41%). Os machos OLSDG também apresentaram hipoprolactinemia (-41%). As fêmeas SDG e OLSDG apresentaram maior estradiol aos 14 dias (+86% e +176%) que se normalizou aos 21 dias, maior colesterolemia (+16%) e as SDG apresentaram maior trigliceridemia (+74%). Aos 21 dias os machos e as fêmeas SDG e OLSDG...

We evaluated the mother's intake of SDG (Diglicoside secoisolariciresinol) and flaxseed oil + SDG upon biochemical and hormonal parameters of lactating female rats and the male and female offspring during lactation. The female lactating rats were divided into: Control (C): feeding a diet with casein; (SDG): feeding diet C added 400mg of SDG/Kg diet; (OLSDG): diet C added 400mg of SDG/Kg diet and 7% of flaxseed oil. Milk samples were obtained on the 14th and 20th days of lactation and the mothers were sacrificed and blood collected by cardiac puncture on the 21st day. Milk and serum were collected for biochemical and hormonal analysis. The male and female offsprings were sacrified on the 14th and 21th day. The hormonal dosages were measured by radioimunassay. The animals were completely eviscerated to analyze body composition. Body mass (BM) and food intake were monitored during all experimental period. The SDG rats showed higher fat mass (+39%) while the OLSDG rats showed lower mineral content (-20%) and triglycerides (TG) serum levels (-39%). The SDG and OLSDG rats showed higher prolactin levels (+339% and +153% respectively) without changes in serum estradiol. On the 14th day of lactation we observed lower lactose (-17%) and protein (-20%) content in the OLSDG rat's milk while in the SDG only lower protein (-21%). From the 13th day of lactation both the males and females OLSDG showed lower BM (-14%, -16%, respectively). On the 14th day the male SDG and OLSDG showed lower fat mass (-24%, -55%, respectively), and the SDG offspring showed higher visceral fat mass (+39%). The SDG male also showed higher TG levels (+105%) and lower prolactin levels (-41%). The OLSDG males also showed lower prolactin serum levels (-41%). The OLSDG female showed higher serum estradiol at 14 days (+86% e +176%), which normalized at 21 days and higher cholesterolemia (+16%) and the SDG female presented higher TG levels (+74%). On day 21th day the male and female SDG and OLSDG...