Bacterial immunostat: mycobacterium tuberculosis lipids and their role in the host immune response

Abstract: The lipid-rich cell wall of Mycobacterium tuberculosis is a dynamic structure that is involved in the regulation of the transport of nutrients, toxic host-cell effector molecules, and anti-tuberculosis drugs. It is therefore postulated to contribute to the long-term bacterial survival in an infected human host. Accumulating evidence suggests that M. tuberculosis remodels the lipid composition of the cell wall as an adaptive mechanism against host-imposed stress. Some of these lipid species (trehalose dimycolate, diacylated sulphoglycolipid, and mannan-based lipoglycans) trigger an immunopathologic response, whereas others (phthiocerol dimycocerosate, mycolic acids, sulpholipid-1, and di-and polyacyltrehalose) appear to dampen the immune responses. These lipids appear to be coordinately expressed in the cell wall of M. tuberculosis during different phases of infection, ultimately determining the clinical fate of the infection. This review summarizes the current state of knowledge on the metabolism, transport, and homeostatic or immunostatic regulation of the cell wall lipids, and their orchestrated interaction with host immune responses that results in bacterial clearance, persistence, or tuberculosis.

Exposure to cetyl pyridinium chloride and loss of integrity of cell wall of mycobacteria.

Background: Cetyl pyridinium chloride (CPC) liquefied sputum was shown to reduce AFB smear positivity presumably damaging cell wall of M. tuberculosis. Settings: National Institute for Research in Tuberculosis, Chennai, (Tamil Nadu). Objective: To assess the cell wall damage of mycobacteria in CPC liquefied sputum, by Transmission Electron Microscopy (TEM) and mycobacteriophage adsorption studies. Methods: Pooled sputum sample from smear positive pulmonary TB patients was homogenized and liquefied with CPC. It was examined in TEM daily for four days, to assess cell wall damage of M. tuberculosis, and photomicrographs were taken. M. smegmatis mc2155, treated with CPC, was infected with mycobacteriophage (phAE129) to study phage adsorption on cell wall and plaque formation. CPC untreated sputum and M. smegmatis formed controls. Results: Photomicrographs showed that cell wall of M. tuberculosis was intact in controls and damaged in CPC preserved sputum for 96 hours. Plaque formation was seen and absent respectively in CPC untreated and treated M. smegmatis cells. Conclusion: Exposure to CPC damaged the cell wall of M. tuberculosis within 96 hours. Mycobacteriophage failed to form plaques after M. smegmatis mc2155 was treated with CPC implying inhibition of phage adsorption on damaged cell wall and thus providing a clue for poor staining and smear positivity in microscopy.

Influência de frações da parede celular de levedura (Saccharomyces cerevisiae) sobre alguns parâmetros nutricionais de ratos em crescimento / Influence of yeast (Saccharomyces cerevisiae) cell wall fractions on some nutritional parameters of growing rats

OBJETIVO: O objetivo deste trabalho foi avaliar a influência das frações de parede celular de levedura (Saccharomyces cerevisiae) sobre alguns parâmetros nutricionais de ratos Wistar em crescimento. MÉTODOS: A biomassa de levedura (Saccharomyces cerevisiae), coletada sem sofrer o processo de termólise, foi recebida da usina São José, Zillo Lorenzetti (Macatuba, SP), em suspensão de, aproximadamente, (20 por cento p/v) de células. O fracionamento da parede celular da levedura foi realizado por extração diferencial, centrifugação e secagem em spray dryer. A importância como fibra da dieta foi determinada em ratos da linhagem Wistar, recém desmamados, por meio das seguintes avaliações: ganho de peso corporal, consumo de dieta (28 dias), quociente de eficiência da dieta, digestibilidade aparente da proteína, quantidade total de fezes, lipídeos e colesterol excretados nas fezes. RESULTADOS: Os animais que receberam a dieta contendo a fração glicana mais manana ganharam menos peso em relação aos demais tratamentos. A dieta com a fração manana foi a que proporcionou maior ganho de peso, seguida pela dieta padrão (AIN-P) e a dieta com 10 por cento de glicana insolúvel. Quanto ao quociente de eficiência da dieta, observou-se, ao longo dos 28 dias, que a dieta com a fração glicana mais manana foi a que apresentou os menores valores. As maiores porcentagens de digestibilidade aparente da proteína foram observadas nas dietas: padrão modificada (AIN-M), padrão (AIN-P) e (M) com 10 por cento da fração manana. As quantidades de lipídeos totais e colesterol excretados nas fezes variaram bastante entre as dietas, sendo que a dieta formulada com 10 por cento de fração manana foi a que promoveu maior excreção do colesterol. CONCLUSÃO: Ao final de 28 dias, os animais que receberam a dieta contendo 10,0 por cento da fração glicana mais manana apresentaram o menor consumo de dieta e ganharam menos peso em relação às demais dietas. A digestibilidade aparente...

OBJECTIVE: The objective of the present work was to assess the nutritional impact of Saccharomyces cerevisiae cell wall fractions on some nutritional parameters in growing Wistar rats. METHODS: Yeast (Saccharomyces cerevisiae) biomass collected without undergoing thermolysis came from the mill São José, Zillo Lorenzetti (Macatuba, SP) in a suspension of approximately 20 percent p/v of cells. Fractionation of the cell wall material was done by differential extraction, centrifugation, and drying in "spray dryer". The importance of the yeast cell components as dietary fibers was assessed in recently weaned Wistar rats by measuring weight gain, diet consumption (28 days), diet efficiency ratio, apparent protein digestibility, total amount of feces and lipids and cholesterol excreted in feces. RESULTS: Rats which were submitted to diets containing glycan plus mannan gained less weight when compared with the other diets. The mannan-containing diet yielded the highest weight gain, followed by the standard AIN diet (S-AIN) and the insoluble glycan diet. Regarding diet efficiency ratio, the diet containing glycan plus mannan produced the lowest values throughout the 28 days. The highest apparent protein digestibility was obtained for the modified standard diet, for the standard AIN diet, as well as for the 10 percent mannan-containing diet (M). Total lipids and cholesterol excreted in the feces varied substantially among the diets. The diet containing 10 percent mannan was the one that promoted the greatest excretion of cholesterol. CONCLUSION: At the end of 28 days, the rats submitted to the glycan plus mannan-containing diets consumed less food and gained less body weight than those submitted to the other diets. Apparent digestibility of all diets was high, 98.6 percent on average. The amounts of total lipids and cholesterol excreted in the feces varied considerably; however, the mannan-containing diet promoted proportionally more cholesterol...

Mechanism of nickel resistance in a cobalt-resistant wall-less mutant of Neurospora crassa (fz; sg; os-1).

A cobalt-resistant wall-less mutant of N. crassa (Cor-sl) characterized previously was also found to be 3-fold more resistant to nickel when compared to the parent wall-less mutant (W-sl). The Cor-sl strain accumulates relatively lower amounts of nickel when compared to W-sl. Sub-cellular fractionation showed significant quantities of nickel to be associated with nuclear and mitochondrial fractions in both the wall-less mutants. However significant differences were observed in vacuolar fractions of W-sl and Cor-sl strains. Fractionation of cell-free extracts on Sephadex G-10 column resolved nickel into two peaks, of which the peak II in Cor-sl constituted 70% of nickel, while the same in W-sl was about 30%. A 3-fold increase in histidine content was observed in case of Cor-sl as compared to W-sl strain, suggesting its role in Ni-resistance.

Fine structural study of the red seaweed Gymnogongrus torulosus (Phyllophoraceae, Rhodophyta)

The present study analyzed several characters of the red seaweed Gymnogongrus torulosus, such as cellular structure of the thallus, cuticle, pit plug and cell wall ultrastructure, and morphology of some organelles like plastids, Golgi bodies and mitochondria. Also, anomalous chloroplasts with thylakoid disorganization were found in medullary cells. The significance of this thylakoid disposition is still unclear. This is one of the first studies focused on the fine structure of a red alga recorded in Argentina.