Microbial-invertebrate interactions and potential for biotechnology

Conclusion As the interactions between marine invertebrates and their bacterial commensals and symbionts are better understood, the application of biotechnology will enhance both environmental and economic benefit. In the immediate future, marine bacteria, either selected or genetically engineered, will play a significant role in enhancing the development of selected invertebrates in aquaculture and in the field. Luck may also favor discovery of mechanisms to suppress the development of biofouling species, perhaps by making it possible to coat submerged surfaces with bacterial films designed to repell larvae and/or interfere with larval morphogenesis. In any case, the future is appealing.     

Colonization of the gut of the blue crab (Callinectes sapidus) by Vibrio cholerae

Attachment of Vibrio cholerae to the mucosal surface of the intestine is considered to be an important virulence characteristic. Vibrio cholerae, an autochthonous member of brackish water and estuarine bacterial communities, also attaches to crustacea, a significant factor in multiplication and survival of V. cholerae in nature. The ability of V. cholerae to attach to the gut wall of the blue crab (Callinectes sapidus) was examined, and attachment was observed only in the hindgut and not the midgut of crabs, confirming a requirement for chitin in the attachment of V. cholerae to invertebrate and zooplankton surfaces. The new finding of attachment of V. cholerae to the hindgut of crabs may be correlated with the epidemiology and transmission of cholera in the aquatic environment. The crab model may also prove useful in elucidating the mechanism(s) of ion transport in crustacea.     

Distribution of sewage indicated by Clostridium perfringens at a deep-water disposal site after cessation of sewage disposal.

Clostridium perfringens, a marker of domestic sewage contamination, was enumerated in sediment samples obtained from the vicinity of the 106-Mile Site 1 month and 1 year after cessation of sewage disposal at this site. C. perfringens counts in sediments collected at the disposal site and from stations 26 nautical miles (ca. 48 km) and 50 nautical miles (ca. 92 km) to the southwest of the site were, in general, more than 10-fold higher than counts from an uncontaminated reference site. C. perfringens counts at the disposal site were not significantly different between 1992 and 1993, suggesting that sewage sludge had remained in the benthic environment at this site. At stations where C. perfringens counts were elevated (i.e., stations other than the reference station), counts were generally higher in the top 1 cm and decreased down to 5 cm. In some cases, C. perfringens counts in the bottom 4 or 5 cm showed a trend of higher counts in 1993 than in 1992, suggesting bioturbation. We conclude that widespread sludge contamination of the benthic environment has persisted for at least 1 year after cessation of ocean sewage disposal at the 106-Mile Site.     

Identical 5S rRNA nucleotide sequence of Vibrio cholerae strains representing temporal, geographical, and ecological diversity.

Enzymatic determination of the nucleotide sequence of 5S rRNA prepared from a Vibrio cholerae non-O1 serovar isolated from a canal in Louisiana in 1978 revealed it to be identical to that of V. cholerae O1 isolated in 1905 from a pilgrim at the E1 Tor quarantine station. The two strains are associated with sharply contrasting habitats. Ranges of variation of 5 to 15% in procaryotic 5S rRNA sequences between species are typical; variation within species may be 2% or greater. Because the 5S rRNA sequences were identical, it is concluded that they have a common phylogenic origin.     

Molecular genetic and phenotypic alteration of Escherichia coli in natural water microcosms containing toxic chemicals

Abstract Microcosms of sterile Chesapeake Bay water were used to study effects of sub-lethal concentrations (1 μl/l) of nitrobenzene, m -cresol, and dibutyl phthalate on Escherichia coli H10407. E. coli remained viable during the 19-day test period in estuarine water, both in the presence and absence of the chemicals, long after it became non-culturable. Analysis of membrane proteins revealed changes in the protein composition. Carbohydrate and amino acid utilization was affected by these changes. Plasmids in E. coli H10407 could not be detected following microcosm exposure. When the cells were transferred to rich medium without toxic chemicals, growth resumed and plasmid bands were again detectable.     

Detection of pericardial effusion by chest roentgenography and electrocardiography versus echocardiography.

To determine the sensitivity and specificity of chest roentgenography and electrocardiography in the detection of pericardial effusion, echocardiography was used as the diagnostic standard. Chest roentgenograms and electrocardiograms of 124 patients, 57 of whom had pericardial effusion, were read without knowledge of the echocardiographic interpretation. The sensitivity of roentgenographic diagnosis was low (20%), as was that of diagnosis from decreased voltage on the electrocardiogram (26%). The specificity of the chest roentgenogram was 89% and that of the low-voltage electrocardiogram 97%. The high specificity of the low-voltage electrocardiogram may have been due in part to the exclusion of obese and emphysematous subjects from the study. When cardiomegaly detected roentgenographically or a low-voltage electrocardiogram or both were considered as evidence of pericardial effusion, sensitivity improved to 82% but specificity declined to 29%. It is concluded the chest roentgenography and electrocardiography are unsatisfactory as screening investigations for the detection of pericardial effusion.     

Sequence analysis of a functional member of the Em gene family from wheat.

We report the complete sequence of one functional member of the Em gene family whose expression in wheat embryos is regulated by a complex set of environmental and developmental controls, including the phytohormone abscisic acid (ABA). The Em coding region contains one short intron, and there is an inverted repeat in the transcribed 3'-flanking region. A 646 bp fragment from the 5' promoter, which was previously shown to direct ABA-regulated expression in transformed tobacco tissue and rice cells, is characterized by: (1) three stretches of between 33 and 73 nucleotides of A/T rich (greater than 86%) boxes, (2) one copy of an eight bp palindrome (CATGCATG) which is identical to the RY repeat found in the 5' promoters of many legume genes expressed during embryo development, (3) 15 copies of a six bp repeat (PuCACGPy), found primarily in the 5' region, and (4) two sequences in the ABA-response region, CGAGCAG and a CACGT motif, both of which are conserved in 5' non-coding regions of other plant genes that are expressed in response to ABA and/or in embryos. These sequence comparisons are discussed in relation to the regulation of Em gene expression and other ABA-regulated genes.     

Effects of isoflurane anesthesia on glucose tolerance and insulin secretion in Yucatan minipigs.

Isoflurane's effect on intravenous glucose tolerance and insulin secretion was studied in six Yucatan minipigs. Unanesthetized animals, with previously placed indwelling venous catheters, were tested while resting comfortably in slings. The same animals were then retested during isoflurane anesthesia. Serum glucose and insulin concentrations were measured at predetermined times in response to an intravenous bolus of dextrose. The glucose disappearance rate (k), baseline plasma insulin concentration, the area under the insulin response curve, and the insulinogenic index were significantly lower in the anesthetized animals than in controls. The results of this study indicate that anesthesia with isoflurane significantly alters the glucose/insulin response to an intravenous glucose tolerance test and, therefore, is unsuitable for studies when glucose tolerance is to be assessed.     

Detection of Vibrio cholerae O1 in the aquatic environment by fluorescent-monoclonal antibody and culture methods.

Vibrio cholerae O1 in plankton samples collected from ponds and rivers between February 1987 and January 1990 in Matlab, Bangladesh, was detected by the fluorescent-monoclonal antibody (FA) technique. Samples were collected at sites which were monitored fortnightly (fixed sites) as well as at sites that were part of a case-control study. FA results were compared with those obtained by conventional culture methods (CM). A total of 876 samples were collected; V. cholerae O1 was detected in 563 samples (64.27%) by the FA method and in 3 samples (0.34%) by CM. Of the fixed-site plankton samples, 439 (63.62%) were positive by FA and none were positive by CM. Of the 93 case sites sampled on the day after the occurrence of a case of cholera, 73 (78.49%) were positive for V. cholerae O1 by FA and 3 (3.2%) were positive by CM. In comparison, of the 93 first-day sample collections at control sites at the time a case of cholera occurred, only 51 (54.83%) were positive by FA and none were positive by CM. From the data, it is concluded that V. cholerae O1 is present throughout the year in the ponds and rivers of Bangladesh that were examined in this study and that V. cholerae can be detected by FA but not always by CM. The FA procedure was found to be very useful in detecting V. cholerae in plankton, with which it was associated and often occurred in large numbers in the nonculturable stage. Thus, studies investigating the significance of the role of environmental factors in the epidemiology of cholera can be performed effectively by using FA. Such studies are in progress.