盐度对稀释平板法研究红树林区土壤微生物数量的影响

在使用稀释平板法分离潮间带红树林及其对照光滩土壤微生物以及计数时,多数情况下使用陈海水制作培养基和稀释水,很少考虑培养基和稀释水的盐度对最终计数结果的影响.使用稀释平板法研究了盐度对福建九龙江口红树林区与深圳福田红树林保护区土壤微生物平板计数的影响,结果表明培养基与稀释水盐度对微生物数量有明显的影响.统计分析显示细菌的海水稀释效果优于淡水,而放线菌与真菌则刚好相反(P<0.05,一个例外).海水不适合配制红树林区土壤微生物平板计数的培养基,从0～35,高盐度的平板培养基会降低微生物的数量,尤其是放线菌的数量,尽管培养基的盐度对真菌影响无规律,但细菌数量在低盐度时比在高盐度和不加氯化钠时要多.根据盐度效应,提出了稀释平板技术应用于潮间带的红树林及其相应光滩时的优化方法,认为细菌应该用海水作无菌稀释水,而放线菌和真菌则应用淡水作稀释水;包括光滩在内的红树林区土壤微生物分离与计数的培养基宜控制较低盐度范围.     

Cultivation of the marine basidiomycete Nia vibrissa (Moore & Meyers)

An isolate of Nia vibrissa was fermented in liquid shake cultures and on agar. Suitable cultivation conditions are a prerequisite for the continuous synthesis of biological active metabolites. The growth response of N. vibrissa to four selected media and several environmental factors, such as salinity, pH and light, was studied. The amount of produced mycelia and the quantity and activity of the organic extracts were parameters for the optimal cultivation method. The ethanolic extracts of the mycelia of N. vibrissa grown in all the investigated nutrient media, showed an influence of the duration of cultivation on the biological activity. A synthetic medium with a pH of 7.5 was the preferred nutrient medium. The addition of wood and incubation under continuous light had no effect on growth but increased the activity of the ethanolic extract. The optimal agar medium salinity for colony growth was in the range between 5 and 25‰. At a salinity of 150‰ growth was not observed.     

A comparison of saline tolerance and sporulation in marine and clinical isolates of Allescheria boydii shear

Summary Two marine and 14 clinical isolates ofA. boydii and its byssoid phase,M. apiospermum, were compared with respect to their saline tolerance, morphological development, and sporulation on various commercial and compounded media. Isolates from sea-water and human infections were morphologically alike, and possessed similar saline tolerance. Most strains had salinity optima near 9, about the salinity of blood. Only marine isolates fruited well on Sabouraud's dextrose agar and other routine mycological media. On a medium containing wood and sea-water, and few soluble organics, 12 strains formed mature ascocarps or synnemata, or both. Low nutrient level media containing wood or cellulosic paper, with or without sea-water, were recommended for the propagation and conservation of sporulating cultures of many saprobic Ascomycetes and synnematous Fungi Imperfecti.     

Low incidence of Vibrio vulnificus among Vibrio isolates from sea water and shellfish of the western Mediterranean coast

A specific search for Vibrio vulnificus in natural marine samples from the Spanish Mediterranean Sea was carried out by nested PCR and cultural approaches using thiosulphate-citrate-bile salts-sucrose agar (TCBS) and cellobiose-polymixin B-colistin agar (CPC), incubated at 40 degrees C, as selective media. Presumptive colonies were identified by PCR using specific primers against 23S rRNA sequences. This species was isolated from sea water and edible bivalves, mainly after preenrichment in alkaline peptone water (APW) at 40 degrees C followed by CPC agar. None of the V. vulnificus isolates identified corresponded to serovar E. Dominant Vibrio species on directly inoculated TCBS plates incubated at 25 degrees C were V. splendidus below 20 degrees C and V. harveyi and V. mediterranei above that temperature. Low percentages of several pathogenic vibrios were recorded but V. vulnificus was never recovered at this incubation temperature. The incidence of this species in the samples studied was lower than that described for other geographical areas, probably due to the high salinity values of the Mediterranean Sea.     

龙须菜在不同盐度胁迫下的琼胶积累及相关生理生化变化的研究

为了探究不同盐度对龙须菜生长、琼胶合成及相关基因表达的影响,研究了15、25和35三种盐度条件下龙须菜的生长速率、琼胶含量、琼胶合成酶α-半乳糖苷酶(GLA)、半乳糖苷转移酶(GAT)、α-1,3-糖脂磺基转移酶(GST)、半乳糖-2,6-硫酸化酶(GAS)的基因表达。结果表明,盐度25时龙须菜生长速率最高,为7.17%/d,高于低盐(15)时的6.27%/d和高盐(35)时的3.57%/d,低盐和高盐都表现出明显的暗呼吸速率上升和光合速率下降。龙须菜培养15d后,在低盐条件下琼胶含量为9.27%,盐度25和高盐分别为6.91%和8.09%。培养第3天时在低盐和高盐下龙须菜中gla基因表达量和酶活都显著高于盐度25的表达量; 15d后在盐度25条件下gla基因表达量仍然最低,但GLA酶活无显著差异。gat基因在低盐条件下先降低后升高,在高盐条件下表达量始终最高,为盐度25的3.03倍。在低盐条件下gst和gas基因都在短期内出现显著下降,但15d后恢复到与正常盐度无显著差异。龙须菜半乳糖含量在高盐条件下相对盐度25显著升高,达到其3.27倍,而在低盐条件下各种单糖含量相对较低,半乳糖含...     

分枝杆菌简化琼脂培养基的研究

报道三种组分简单、制备方便的简化琼脂培养基.试验结果表明:7个标准菌株在简化琼脂培养基309A和309C上的生长速度和数量均相似或优于改良罗氏培养基和92号土豆汤琼脂培养基.简化琼脂培养基309C和309A可用于结核杆菌分离和药敏试验.     

Comparison of Brilliant Green Agar and Hektoen Enteric Agar Media in the Isolation of Salmonellae from Food Products

Brilliant Green (BG) agar and Hektoen enteric (HE) agar media were compared for their efficiency in isolating salmonellae from various food products. Of the 11,226 food specimens examined, 1,662 (or 14.9%) yielded salmonellae. Of this number, 1,475 (88.7%) were recovered from BG agar and 1,315 (79.1%) were recovered from HE agar media. The results indicate that BG agar is more effective in isolating salmonellae from food products. A smaller subsidiary study showed HE agar to be more selective than BG agar. Four hundred ten specimens yielded 92 nonlactose-fermenting isolants other than salmonellae on BG agar and only 11 such isolants on HE agar.     

Comparison of seven plating media for enumeration of Listeria spp.

The suitability of seven media for the enumeration of Listeria spp. was evaluated at 30 degrees C for 48 h. The media tested were (i) the original McBride Listeria agar formulation (with glycine); (ii) modified McBride agar containing glycine anhydride; (iii) LiCl-phenylethanol-moxalactam (LPM) agar; (iv) acriflavine-ceftazidime agar; (v) Rodriguez isolation agar (RISA); (vi) modified Vogel-Johnson (MVJ) agar; (vii) cyclohexanedione-nalidixic acid-phenylethanol agar; and tryptose agar as control. A total of 66 organisms were used including 11 Listeria monocytogenes strains and 5 other Listeria spp. For L. monocytogenes strains only, all media performed highly similarly. Of the other Listeria spp., only two grew on MVJ agar and three each grew on LPM and RISA. Only LPM agar inhibited the 50 non-listeriae, including five yeasts, while MVJ agar inhibited all but one yeast. The McBride Listeria agar formulation that contained glycine anhydride was less selective than the original. When pure cultures of 10 bacteria (including one L. monocytogenes strain) were combined and plated on four media, L. monocytogenes colonies were easiest to enumerate on MVJ agar, followed by LPM and RISA. These media ranked in the same order when plated with homogenates of various foods to which was added L. monocytogenes Scott A, but LPM agar was the best overall since Scott A was inhibited by MVJ. Upon microscopic examination of listerial colonies from the plating media, atypical cell morphology was noted with cells being about twofold in size on LPM, MVJ, and acriflavine-ceftazidime agars. Overall, LPM agar was the most suitable of the media tested even though it was inhibitory to Listeria grayi and Listeria murrayi.     

分枝杆菌全合成琼脂培养基的研究

本文报道了一种适合常见致病分枝杆菌生长的全合成固体琼脂培养基体系。它为实验室研究分枝杆菌的营养生理、生化特性、遗传变异、药理和耐药机制提供了一种新工具,也为研制更加满意的分枝杆菌培养基创造了条件。试验过的大多数非典型分枝杆菌,在全合成琼脂培养基上比在罗氏培养基上生长快,生长量少于或等于罗氏培养基。标准牛型株的细胞群体中,仅有少量细胞能在全合成琼脂培养基上生长。鸟型．胞内和偶发等分枝杆菌标准株在全合成琼脂培养基上产生两种不同的菌落。     

Salinity Effects on Photosynthesis, Carbon Allocation, and Nitrogen Assimilation in the Red Alga, Gelidium coulteri

The long-term effects of altered salinities on the physiology of the intertidal red alga Gelidium coulteri Harv. were assessed. Plants were transfered from 30 grams per liter salinity to media with salinities from 0 to 50 grams per liter. Growth rate, agar, photosynthesis, respiration, and various metabolites were quantified after 5 days and 5 weeks adaptation. After 5 days, growth rates were lower for plants at all altered salinities. Growth rates recovered from these values with 5 weeks adaptation, except for salinities of 10 grams per liter and below, where tissues bleached and died. Photosynthetic O₂ evolution was lower than control values at both higher and lower salinities after 5 days and did not change over time. Carbon fixation at the altered salinities was unchanged after 5 days, but decreased below 25 grams per liter and above 40 grams per liter after 5 weeks. Respiration increased at lower salinities. Phycobili-protein and chlorophyll were lower for all altered salinities after 5 days. These decreases continued at lower salinities, then were stable after 5 weeks. Chlorophyll recovered over time at higher salinities. Decreases in protein at lower salinities were quantitatively attributable to phycobili-protein loss. Total N levels and C:N ratios were nearly constant across all salinities tested. Carbon flow into glutamate and aspartate decreased with both decreasing and increasing salinities. Glycine, serine, and glycolate levels increased with both increasing and decreasing salinity, indicating a stimulation of photorespiration. The cell wall component agar increased with decreasing salinity, although biosynthesis was inhibited at both higher and lower salinities. The storage compound floridoside increased with increasing salinity. The evidence suggests stress responses to altered salinities that directly affected photosynthesis, respiration, and nitrogen assimilation and indirectly affected photosynthate flow. At low salinities, respiration and photorespiration exceeded photosynthesis with lethal results. At higher salinities, although photosynthesis was inhibited, respiration was low and carbon fixation adequate to offset increased photorespiration.     

Evaluation of several selective media for recovery of Aeromonas hydrophila from polluted waters

Eleven media were studied for their suitability in the selective isolation of Aeromonas hydrophila. Preliminary results showed that five of them (inositol-brilliant green-bile salts agar, bile salts-brilliant green agar, Rimler-Shotts agar, xylose-sodium deoxycholate-citrate agar, and dextrin-fuchsin-sulfite agar) allowed the growth of several microorganisms that are usually present in the same samples in which A. hydrophila is found. Six media (mA agar, modified Rimler-Shotts agar, DNase-toluidine blue-ampicillin agar, Pril-xylose-ampicillin agar, MacConkey-trehalose agar, and starch-bile salts agar) were selected for evaluation as recovery selective media on the basis of their efficiency in the isolation of A. hydrophila from natural water samples. mA agar showed the best recovery rate and also an acceptable specificity, but its selectivity was low. Another medium that can be considered is DNase-toluidine blue-ampicillin agar, which showed good accuracy, but its specificity was low.     

Evaluation of several selective media for recovery of Aeromonas hydrophila from polluted waters.

Eleven media were studied for their suitability in the selective isolation of Aeromonas hydrophila. Preliminary results showed that five of them (inositol-brilliant green-bile salts agar, bile salts-brilliant green agar, Rimler-Shotts agar, xylose-sodium deoxycholate-citrate agar, and dextrin-fuchsin-sulfite agar) allowed the growth of several microorganisms that are usually present in the same samples in which A. hydrophila is found. Six media (mA agar, modified Rimler-Shotts agar, DNase-toluidine blue-ampicillin agar, Pril-xylose-ampicillin agar, MacConkey-trehalose agar, and starch-bile salts agar) were selected for evaluation as recovery selective media on the basis of their efficiency in the isolation of A. hydrophila from natural water samples. mA agar showed the best recovery rate and also an acceptable specificity, but its selectivity was low. Another medium that can be considered is DNase-toluidine blue-ampicillin agar, which showed good accuracy, but its specificity was low.     

Development of a method for the quantitative assessment of microorganism sensitivity to antibiotics using discs. The study of different nutrient media for determining microorganism sensitivity to antibiotics

Five nutrient media used for determination of microbial sensitivity to antibiotics, i.e. beaf-peptone agar, Hottinger pancreatic beaf infusion agar, sprat hydrolysate nutrient agar of the Dagestan Research Institute of Nutrient Media, Muller-Chintone agar from Bulgaria and "Oxoid" agar for determination of microbial sensitivity were studied comparatively. The media were compared with respect to the growth density with the use of different test-cultures and the clearance of the inhibition growth zones around the discs containing different antibiotics. The best results were obtained with the use of sprat hydrolysate nutrient agar. Further studies on the medium standardization are necessary.     

Calcium and magnesium in Mueller-Hinton agar and their influence on disk diffusion susceptibility results

Concentrations of calcium and magnesium were determined for 39 lots of media, including broth and agar media used for susceptibility tests and plain agar. In addition, the effect that media with and without physiological levels of these divalent cations would have on the disk diffusion susceptibility of 21 strains ofPseudomonas aeruginosa to four antimicrobics was also ascertained. Mueller-Hinton agar showed a wide variation in calcium and magnesium content. Mueller-Hinton broth contained lower concentrations of calcium and magnesium, and there was little lot-to-lot variation. Lots of Mueller-Hinton agar with higher concentrations of calcium and magnesium yielded smaller zone diamaters than those with lower concentrations. Even at equal cation concentration, zones of inhibition varied from lot to lot. Since the addition of calcium and magnesium to Mueller-Hinton agar to obtain a predetermined level did not result in equivalent zone diameters, performance testing of susceptibility media is recommended.     

Comparison of Media for Direct Isolation and Transport of Shigellae from Fecal Specimens

Xylose-lysine-deoxycholate (XLD) agar, SS agar, and MacConkey agar for isolating shigellae from fecal specimens were compared. XLD agar was superior to both SS agar and MacConkey agar for isolating Shigella sonnei, and both XLD and SS agar were superior to MacConkey agar for isolating S. flexneri. Direct plating of the fecal specimens in the field resulted in a greater yield of shigellae as compared to transporting specimens to the laboratory either in holding media or enrichment broth. Buffered glycerol saline was superior to other transport media evaluated, yielding 83% of shigella isolates when plated within 48 hr as compared to direct plating. The combination of XLD agar and SS agar is recommended for direct isolation of shigellae, and, whenever possible, these solid media should be taken to the bedside and inoculated directly.     

Effect of selective media on loss of congo red binding inShigella flexneri

Summary The effect of growth ofShigella flexneri on various selective media on retention of congo red (CR) binding ability was determined to evaluate the effectiveness of isolation techniques regarding maintenance of the virulence plasmid. WhenS. flexneri was surface-plated onto selective agars and the resulting colonies replica plated onto CR plates, no white colonies indicative of loss of virulence were found despite repeated trials. However, whenS. flexneri was grown in liquid media (agar was removed from agar-containing media by centrifugation), white colonies were found upon plating onto CR plates. Most common selective media for shigellae produced fewer than 5–10 white colonies/1000 red colonies. However, growth in broth prepared from violet red bile agar, desoxycholate citrate agar, and SS agar gave more than 100 white colonies/1000 red colonies. Loss of CR binding was demonstrated whenS. flexneri was grown in broth containing tergitol 7, sodium dodecyl sulfate, bile salts #3, crystal violet, eosin y or methylen blue. However, concentrations of selective agents that led to loss of CR binding were much higher than those used in selective media. Results indicate that under usual conditions of isolation ofS. flexneri from food and clinical specimens, CR binding appears to be a relatively stable character with most selective media; however, use of violet red bile agar, desoxycholate citrate agar, and SS agar may lead to substantial loss of congo red binding indicating that the isolates may not be virulent.     

Enumeration of Clostridium perfringens spores in groundwater samples: comparison of six culture media

In order to investigate the ability of Fluorocult-supplemented TSC agar (TSCF (Fluorocult supplemented TSC-agar): prepared from Tryptose Sulfite Cycloserine Agar Base (Merck), D-cycloserine (Fluka Chemika, USA), and fluorocult TSC-Agar supplement (Merck)) for detecting spores of Clostridium perfringens in water, we analyzed groundwater samples, pretreated by heating to 80 degrees C/5 min, using this fluorogenic medium together with five other media: mCP agar (Panreac; Cultimed), TSC agar (Merck, Germany), TSN agar (Merck), and SPS agar (BBL, USA) by the membrane filtration technique, and Wilson-Blair agar (WB) following the still-in-force Spanish official method. Variance analysis of the data obtained shows statistically significant differences in the counts obtained between media employed in this work. The C. perfringens spore counts on mCP agar were significantly lower (P<0.05) than the corresponding values of TSC, TSCF, SPS, and WB media. No statistically significant differences were found between C. perfringens spore counts on TSCF compared with those of other methods used. On the other hand, the identification of typical and atypical colonies isolated from all media demonstrated that fluorogenic TSC agar was the most specific medium for C. perfringens spore recovery in groundwater samples. Additionally, the results obtained indicate that mCP agar, which is the reference method in the European Union, is not suitable medium for recovering C. perfringens spores from groundwater samples.     

The suitability of four media for enumerating Aeromonas spp. from environmental samples

Starch ampicillin agar (SA), dextrin fuchsin sulphite agar (DFS) and blood agar with 10 mg (BA-10) and 30 mg (BA-30) ampicillin/l, respectively, were evaluated for enumeration of Aeromonas spp. from environmental samples. Recovery from pure cultures was excellent on all media except for ampicillin-sensitive strains on the ampicillin-containing media. With natural samples, the ability to differentiate Aeromonas from the background microflora was best on SA agar where 85% presumptive Aeromonas colonies were confirmed, compared with 18% on DFS, 36% on BA-10 and 40% on BA-30. Prolonged incubation caused a decrease in the differentiating ability.     

Effect of irradiation on the protein profile,protein content,and quality of agar from <Emphasis Type="Italic">Gracilaria asiatica</Emphasis> Zhang et Xia (Rhodophyta)

There are about 15 species of Gracilaria reported in Vietnam. Of these, Gracilaria asiatica Zhang et Xia is being cultivated on a large scale in Northern Vietnam, which has a subtropical climate. During the rainy season, from May to October, the growth of G. asiatica is drastically reduced or even ceases due to very low salinity and high temperature. Therefore, it is important to improve the tolerance of G. asiatica to a wide range of salinity and temperatures. This paper presents the results of research on strain improvement of G. asiatica using irradiation and selection media. Three irradiation doses of 20, 60, and 100 krad were tested against the control (with no irradiation). Afterward, the seaweed biomass was cultivated on a selected medium, ESS-1, containing NaCl in concentrations of 23‰ (C1) and 0‰ (C2). The results showed that a higher survival rate of G. asiatica was observed with the 20- and 60-krad doses. The protein content and composition of selected seaweeds were analyzed and compared with the control. SDS-PAGE showed no remarkable difference in the protein composition between the control and irradiated samples. However, the 67-kDa protein band of seaweed treated with 20 and 60 krad, then grown on ESS-1 medium with 23% NaCl, had a higher density than other samples. This protein was reported to play an important role in G. asiatica, by enhancing its tolerance to variable salinity and temperature. Although the organic and inorganic content of all samples remained almost the same, the content and quality of agar extracted from irradiated seaweeds were higher than those of the controls. Due to the high amount of 3.6 anhydro-α-L-galactose combined with low amounts of sulfate found in irradiated seaweeds, the freezing and melting points of extracted agar were lower. Eventually, this resulted in higher condensation and better quality of agar, such as in its gel-forming ability. The quality of fluid agar extracted from selected seaweeds improved as shown in the remarkable decrease in Ca²⁺, Mg²⁺, and total Fe ion content, thus lowering its melting point compared with the control. Presented at the 6th Meeting of the Asian Pacific Society of Applied Phycology, Manila, Philippines.     

Relationship between gene expression of UDP-glucose pyrophosphorylase and agar yield in Gracilariopsis lemaneiformis (Rhodophyta)

UDP-glucose pyrophosphorylase (UGPase) is an enzyme involved in the biosynthesis of UDP-D-galactose, a subunit of agar in red seaweeds. The relationship between agar content and expression levels of the UGPase encoding gene (glugp) was studied in thalli under different treatment conditions using a quantitative real-time PCR-based method (qPCR). Moreover, this qPCR method for the measurement of glugp expression was also applied to commercial varieties of Gracilariopsis lemaneiformis, a red macroalga, in order to examine its reliability on material obtained from field cultivation. Both the agar content and glugp gene expression in G. lemaneiformis grown under low salinity (17?‰) conditions for 1 week showed a slight increase in comparison with the control group (33?‰ salinity, natural salinity of seawater), but the difference was not statistically significant (P?>?0.05). However, when the culture time was extended to 2 weeks, the increase in both the agar yield and glugp expression became significant (P?glugp expression (P?>?0.05). Our results suggest that glugp gene expression and agar content are highly positively correlated and that the measurement of glugp expression, using only a small amount of thalli material, may be an efficient approach to evaluate agar content. In addition, both the agar content and glugp expression in cultivars 981, 07-2, and ZC differed significantly from those of MT-18. The findings of this study suggest that UGPase may be involved in agar biosynthesis and indicate that glugp gene expression could be a fairly reliable molecular marker to reflect the agar content of strains during breeding and selection of G. lemaneiformis.