Engineering topics

Reiter, Michael

Publications and source records attributed to Reiter, Michael.

4 records

DOE OSTI2018

Improving formaldehyde consumption drives methanol assimilation in engineered E. coli

Abstract Due to volatile sugar prices, the food vs fuel debate, and recent increases in the supply of natural gas, methanol has emerged as a promising feedstock for the bio-based economy. However, attempts to engineer Escherichia coli to metabolize methanol have achieved limited success. Here, we provide a rigorous systematic analysis of several potential pathway bottlenecks. We show that regeneration of ribulose 5-phosphate in E. coli is insufficient to sustain methanol assimilation, and overcome this by activating the sedoheptulose bisphosphatase variant of the ribulose monophosphate pathway. By leveraging the kinetic isotope effect associated with deuterated methanol as a chemical probe, we further demonstrate that under these conditions overall pathway flux is kinetically limited by methanol dehydrogenase. Finally, we identify NADH as a potent kinetic inhibitor of this enzyme. These results provide direction for future engineering strategies to improve methanol utilization, and underscore the value of chemical biology methodologies in metabolic engineering.

59 BASIC BIOLOGICAL SCIENCES↗

NASA NTRS1992

How to securely replicate services

A method is presented for constructing replicated services that retain their availability and integrity despite several servers and clients corrupted by an intruder, in addition to others failing benignly. More precisely, a service is replicated by n servers in such a way that a correct client will accept a correct server's response if, for some prespecified parameter k, at least k servers are correct and fewer than k servers are corrupt. The issue of maintaining causality among client requests is also addressed. A security breach resulting from an intruder's ability to effect a violation of causality in the sequence of requests processed by the service is illustrated. An approach to counter this problem is proposed that requires fewer than k servers to be corrupt and that is live if at least k+b servers are correct, where b is the assumed maximum total number of corrupt servers in any system run. An important and novel feature of these schemes is that the client need not be able to identify or authenticate even a single server. Instead, the client is required only to possess at most two public keys for the service. The practicality of these schemes is illustrated through a discussion of several issues pertinent to their implementation and use, and their intended role in a secure version of the Isis system is also described.

Reiter, Michael↗

NASA NTRS1992

How to securely replicate services (preliminary version)

A method is presented for constructing replicated services that retain their availability and integrity despite several servers and clients being corrupted by an intruder, in addition to others failing benignly. More precisely, a service is replicated by 'n' servers in such a way that a correct client will accept a correct server's response if, for some prespecified parameter, k, at least k servers are correct and fewer than k servers are correct. The issue of maintaining causality among client requests is also addressed. A security breach resulting from an intruder's ability to effect a violation of causality in the sequence of requests processed by the service is illustrated. An approach to counter this problem is proposed that requires that fewer than k servers are corrupt and, to ensure liveness, that k is less than or = n - 2t, where t is the assumed maximum total number of both corruptions and benign failures suffered by servers in any system run. An important and novel feature of these schemes is that the client need not be able to identify or authenticate even a single server. Instead, the client is required only to possess at most two public keys for the service.

Reiter, Michael↗

NASA NTRS1992

Integrating security in a group oriented distributed system

A distributed security architecture is proposed for incorporation into group oriented distributed systems, and in particular, into the Isis distributed programming toolkit. The primary goal of the architecture is to make common group oriented abstractions robust in hostile settings, in order to facilitate the construction of high performance distributed applications that can tolerate both component failures and malicious attacks. These abstractions include process groups and causal group multicast. Moreover, a delegation and access control scheme is proposed for use in group oriented systems. The focus is the security architecture; particular cryptosystems and key exchange protocols are not emphasized.

Reiter, Michael↗