A gene with substantial sequence similarity to the mreB morphogene of Bacillus subtilis has been identified at 302؇ on the chromosomal map by A. Decatur, B. Kunkel, and R. Losick (Harvard University; personal communication). Our characterization has revealed that the protein product of this determinant (termed mbl for mreB-like) is 55 and 53% identical in sequence to the MreB proteins of B. subtilis and Escherichia coli, respectively. The protein is 86% identical to a protein identified as MreB from Bacillus cereus, suggesting that the B. cereus protein is actually Mbl. Insertional inactivation of mbl indicated that this gene is not essential for cell viability or sporulation. Cells bearing mutant mbl alleles display a decreased growth rate and an altered cellular morphology. The cells appear bloated and are frequently twisted. Intergenic suppressor mutations which restore the growth rate to an approximately normal level arise within the mutant population. A second site mutation, designated som-1, was mapped to the hisA-mbl region of the chromosome by transduction.The mre operon of Escherichia coli consists of five genes, mreBCD, orfE, and cafA (10,25,(33)(34)(35)(36). The mreBCD genes are associated with cell shape determination and sensitivity to the aminidopenicillin mecillinam. A point mutation within mreB or a deletion of mreBCD results in a morphological shift in the cell population with the formation of spherical cells. The mreB determinant encodes a 37,000-kDa protein which shows significant sequence similarity to the DnaK protein, as well as to other members of the Hsp70 superfamily, and to the FtsA cell division-associated protein (3, 13). Inactivation of the MreB protein results in an increased level of the FtsI protein, the septation-specific penicillin-binding protein 3 (36). The increased FtsI presumably results in hyperseptation activity and hence spherical-cell formation (22). The introduction of mreB on a multicopy plasmid results in the cells becoming filamentous and an accompanying decrease in FtsI (36). On the basis of these observations, Wachi et al. have postulated that the MreB protein acts as a negative regulator of FtsI (36).The MreB homolog of Bacillus subtilis is contained within the divIVB minicell operon (19,20,32). This operon contains the mreBCD determinants as well as the minCD minicell-associated genes. Immediately upstream of divIVB lies maf, the apparent homolog of orfE of the E. coli mre operon (5). The B. subtilis MreB protein has substantial amino acid sequence similarity (56.8% identity, 67% similarity) with its E. coli counterpart. A difference between the E. coli and B. subtilis mreB determinants with regard to inactivation has been noted. Loss of MreB function in E. coli results in viable spherical cells, whereas attempts to inactivate the mreB determinant of B. subtilis have been unsuccessful (20,32). MreB function is apparently required for the maintenance of cell viability in this gram-positive bacterium.The mreB determinant of B. subtilis was identified by amino acid...
The Bacillus subtilis homolog of the Escherichia coli morphogene orfE (of the mre operon) has been identified. The determinant is located on the chromosome immediately upstream of the mreBCD-minCD (divIVB) operon. The Maf protein shares substantial amino acid sequence identity with the E. coli OrfE protein. Introduction of the B. subtilis maf determinant on a multicopy plasmid into B. subtilis cells results in an inhibition of septation, which leads to extensive filamentation and loss of viability in the transformed cell population. Insertional inactivation of maf indicated that this gene is not essential for cell division.
Unripe wood apple fruit is generally free from visible fungal growth before and at harvest but a succession of fungi appears on the fruit shell, and sometimes in the pulp, during ripening. A TLC‐Cladosporium bioassay of the chloroform extract taken from unripe fruit shell demonstrated three inhibition areas. Similar extracts from stem‐bark and root‐bark produced these three, and one additional, inhibition areas. The four compounds responsible for inhibition were identified as psoralene, xanthotoxin, 2,6‐dimethoxybenzoquinone and osthenol. Concentrations of the three antifungal compounds on unripe fruit shell increased during the first 4 days after harvest and then declined. They remained much below those required to inhibit the development of three fungi on TLC plates. Titratable acidity of the unripe fruit pulp was high but decreased by about 50% during ripening. Levels of reducing sugars were very low in the unripe fruit pulp but increased by about five times during ripening. Levels also increased in the fruit shell and its washings. The possible role of these factors in restricting fungal growth in unripe fruits is discussed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.